Index: frontend/node_modules/emittery/index.js
===================================================================
--- frontend/node_modules/emittery/index.js	(revision 9af201e94b5a79beb92a30858fc54de4bc3b9449)
+++ frontend/node_modules/emittery/index.js	(revision 9af201e94b5a79beb92a30858fc54de4bc3b9449)
@@ -0,0 +1,408 @@
+'use strict';
+
+const anyMap = new WeakMap();
+const eventsMap = new WeakMap();
+const producersMap = new WeakMap();
+const anyProducer = Symbol('anyProducer');
+const resolvedPromise = Promise.resolve();
+
+const listenerAdded = Symbol('listenerAdded');
+const listenerRemoved = Symbol('listenerRemoved');
+
+function assertEventName(eventName) {
+	if (typeof eventName !== 'string' && typeof eventName !== 'symbol') {
+		throw new TypeError('eventName must be a string or a symbol');
+	}
+}
+
+function assertListener(listener) {
+	if (typeof listener !== 'function') {
+		throw new TypeError('listener must be a function');
+	}
+}
+
+function getListeners(instance, eventName) {
+	const events = eventsMap.get(instance);
+	if (!events.has(eventName)) {
+		events.set(eventName, new Set());
+	}
+
+	return events.get(eventName);
+}
+
+function getEventProducers(instance, eventName) {
+	const key = typeof eventName === 'string' || typeof eventName === 'symbol' ? eventName : anyProducer;
+	const producers = producersMap.get(instance);
+	if (!producers.has(key)) {
+		producers.set(key, new Set());
+	}
+
+	return producers.get(key);
+}
+
+function enqueueProducers(instance, eventName, eventData) {
+	const producers = producersMap.get(instance);
+	if (producers.has(eventName)) {
+		for (const producer of producers.get(eventName)) {
+			producer.enqueue(eventData);
+		}
+	}
+
+	if (producers.has(anyProducer)) {
+		const item = Promise.all([eventName, eventData]);
+		for (const producer of producers.get(anyProducer)) {
+			producer.enqueue(item);
+		}
+	}
+}
+
+function iterator(instance, eventNames) {
+	eventNames = Array.isArray(eventNames) ? eventNames : [eventNames];
+
+	let isFinished = false;
+	let flush = () => {};
+	let queue = [];
+
+	const producer = {
+		enqueue(item) {
+			queue.push(item);
+			flush();
+		},
+		finish() {
+			isFinished = true;
+			flush();
+		}
+	};
+
+	for (const eventName of eventNames) {
+		getEventProducers(instance, eventName).add(producer);
+	}
+
+	return {
+		async next() {
+			if (!queue) {
+				return {done: true};
+			}
+
+			if (queue.length === 0) {
+				if (isFinished) {
+					queue = undefined;
+					return this.next();
+				}
+
+				await new Promise(resolve => {
+					flush = resolve;
+				});
+
+				return this.next();
+			}
+
+			return {
+				done: false,
+				value: await queue.shift()
+			};
+		},
+
+		async return(value) {
+			queue = undefined;
+
+			for (const eventName of eventNames) {
+				getEventProducers(instance, eventName).delete(producer);
+			}
+
+			flush();
+
+			return arguments.length > 0 ?
+				{done: true, value: await value} :
+				{done: true};
+		},
+
+		[Symbol.asyncIterator]() {
+			return this;
+		}
+	};
+}
+
+function defaultMethodNamesOrAssert(methodNames) {
+	if (methodNames === undefined) {
+		return allEmitteryMethods;
+	}
+
+	if (!Array.isArray(methodNames)) {
+		throw new TypeError('`methodNames` must be an array of strings');
+	}
+
+	for (const methodName of methodNames) {
+		if (!allEmitteryMethods.includes(methodName)) {
+			if (typeof methodName !== 'string') {
+				throw new TypeError('`methodNames` element must be a string');
+			}
+
+			throw new Error(`${methodName} is not Emittery method`);
+		}
+	}
+
+	return methodNames;
+}
+
+const isListenerSymbol = symbol => symbol === listenerAdded || symbol === listenerRemoved;
+
+class Emittery {
+	static mixin(emitteryPropertyName, methodNames) {
+		methodNames = defaultMethodNamesOrAssert(methodNames);
+		return target => {
+			if (typeof target !== 'function') {
+				throw new TypeError('`target` must be function');
+			}
+
+			for (const methodName of methodNames) {
+				if (target.prototype[methodName] !== undefined) {
+					throw new Error(`The property \`${methodName}\` already exists on \`target\``);
+				}
+			}
+
+			function getEmitteryProperty() {
+				Object.defineProperty(this, emitteryPropertyName, {
+					enumerable: false,
+					value: new Emittery()
+				});
+				return this[emitteryPropertyName];
+			}
+
+			Object.defineProperty(target.prototype, emitteryPropertyName, {
+				enumerable: false,
+				get: getEmitteryProperty
+			});
+
+			const emitteryMethodCaller = methodName => function (...args) {
+				return this[emitteryPropertyName][methodName](...args);
+			};
+
+			for (const methodName of methodNames) {
+				Object.defineProperty(target.prototype, methodName, {
+					enumerable: false,
+					value: emitteryMethodCaller(methodName)
+				});
+			}
+
+			return target;
+		};
+	}
+
+	constructor() {
+		anyMap.set(this, new Set());
+		eventsMap.set(this, new Map());
+		producersMap.set(this, new Map());
+	}
+
+	on(eventNames, listener) {
+		assertListener(listener);
+
+		eventNames = Array.isArray(eventNames) ? eventNames : [eventNames];
+		for (const eventName of eventNames) {
+			assertEventName(eventName);
+			getListeners(this, eventName).add(listener);
+
+			if (!isListenerSymbol(eventName)) {
+				this.emit(listenerAdded, {eventName, listener});
+			}
+		}
+
+		return this.off.bind(this, eventNames, listener);
+	}
+
+	off(eventNames, listener) {
+		assertListener(listener);
+
+		eventNames = Array.isArray(eventNames) ? eventNames : [eventNames];
+		for (const eventName of eventNames) {
+			assertEventName(eventName);
+			getListeners(this, eventName).delete(listener);
+
+			if (!isListenerSymbol(eventName)) {
+				this.emit(listenerRemoved, {eventName, listener});
+			}
+		}
+	}
+
+	once(eventNames) {
+		return new Promise(resolve => {
+			const off = this.on(eventNames, data => {
+				off();
+				resolve(data);
+			});
+		});
+	}
+
+	events(eventNames) {
+		eventNames = Array.isArray(eventNames) ? eventNames : [eventNames];
+		for (const eventName of eventNames) {
+			assertEventName(eventName);
+		}
+
+		return iterator(this, eventNames);
+	}
+
+	async emit(eventName, eventData) {
+		assertEventName(eventName);
+
+		enqueueProducers(this, eventName, eventData);
+
+		const listeners = getListeners(this, eventName);
+		const anyListeners = anyMap.get(this);
+		const staticListeners = [...listeners];
+		const staticAnyListeners = isListenerSymbol(eventName) ? [] : [...anyListeners];
+
+		await resolvedPromise;
+		await Promise.all([
+			...staticListeners.map(async listener => {
+				if (listeners.has(listener)) {
+					return listener(eventData);
+				}
+			}),
+			...staticAnyListeners.map(async listener => {
+				if (anyListeners.has(listener)) {
+					return listener(eventName, eventData);
+				}
+			})
+		]);
+	}
+
+	async emitSerial(eventName, eventData) {
+		assertEventName(eventName);
+
+		const listeners = getListeners(this, eventName);
+		const anyListeners = anyMap.get(this);
+		const staticListeners = [...listeners];
+		const staticAnyListeners = [...anyListeners];
+
+		await resolvedPromise;
+		/* eslint-disable no-await-in-loop */
+		for (const listener of staticListeners) {
+			if (listeners.has(listener)) {
+				await listener(eventData);
+			}
+		}
+
+		for (const listener of staticAnyListeners) {
+			if (anyListeners.has(listener)) {
+				await listener(eventName, eventData);
+			}
+		}
+		/* eslint-enable no-await-in-loop */
+	}
+
+	onAny(listener) {
+		assertListener(listener);
+		anyMap.get(this).add(listener);
+		this.emit(listenerAdded, {listener});
+		return this.offAny.bind(this, listener);
+	}
+
+	anyEvent() {
+		return iterator(this);
+	}
+
+	offAny(listener) {
+		assertListener(listener);
+		this.emit(listenerRemoved, {listener});
+		anyMap.get(this).delete(listener);
+	}
+
+	clearListeners(eventNames) {
+		eventNames = Array.isArray(eventNames) ? eventNames : [eventNames];
+
+		for (const eventName of eventNames) {
+			if (typeof eventName === 'string' || typeof eventName === 'symbol') {
+				getListeners(this, eventName).clear();
+
+				const producers = getEventProducers(this, eventName);
+
+				for (const producer of producers) {
+					producer.finish();
+				}
+
+				producers.clear();
+			} else {
+				anyMap.get(this).clear();
+
+				for (const listeners of eventsMap.get(this).values()) {
+					listeners.clear();
+				}
+
+				for (const producers of producersMap.get(this).values()) {
+					for (const producer of producers) {
+						producer.finish();
+					}
+
+					producers.clear();
+				}
+			}
+		}
+	}
+
+	listenerCount(eventNames) {
+		eventNames = Array.isArray(eventNames) ? eventNames : [eventNames];
+		let count = 0;
+
+		for (const eventName of eventNames) {
+			if (typeof eventName === 'string') {
+				count += anyMap.get(this).size + getListeners(this, eventName).size +
+					getEventProducers(this, eventName).size + getEventProducers(this).size;
+				continue;
+			}
+
+			if (typeof eventName !== 'undefined') {
+				assertEventName(eventName);
+			}
+
+			count += anyMap.get(this).size;
+
+			for (const value of eventsMap.get(this).values()) {
+				count += value.size;
+			}
+
+			for (const value of producersMap.get(this).values()) {
+				count += value.size;
+			}
+		}
+
+		return count;
+	}
+
+	bindMethods(target, methodNames) {
+		if (typeof target !== 'object' || target === null) {
+			throw new TypeError('`target` must be an object');
+		}
+
+		methodNames = defaultMethodNamesOrAssert(methodNames);
+
+		for (const methodName of methodNames) {
+			if (target[methodName] !== undefined) {
+				throw new Error(`The property \`${methodName}\` already exists on \`target\``);
+			}
+
+			Object.defineProperty(target, methodName, {
+				enumerable: false,
+				value: this[methodName].bind(this)
+			});
+		}
+	}
+}
+
+const allEmitteryMethods = Object.getOwnPropertyNames(Emittery.prototype).filter(v => v !== 'constructor');
+
+Object.defineProperty(Emittery, 'listenerAdded', {
+	value: listenerAdded,
+	writable: false,
+	enumerable: true,
+	configurable: false
+});
+Object.defineProperty(Emittery, 'listenerRemoved', {
+	value: listenerRemoved,
+	writable: false,
+	enumerable: true,
+	configurable: false
+});
+
+module.exports = Emittery;