Index: frontend/node_modules/html-encoding-sniffer/lib/html-encoding-sniffer.js
===================================================================
--- frontend/node_modules/html-encoding-sniffer/lib/html-encoding-sniffer.js	(revision 9af201e94b5a79beb92a30858fc54de4bc3b9449)
+++ frontend/node_modules/html-encoding-sniffer/lib/html-encoding-sniffer.js	(revision 9af201e94b5a79beb92a30858fc54de4bc3b9449)
@@ -0,0 +1,295 @@
+"use strict";
+const whatwgEncoding = require("whatwg-encoding");
+
+// https://html.spec.whatwg.org/#encoding-sniffing-algorithm
+module.exports = (buffer, { transportLayerEncodingLabel, defaultEncoding = "windows-1252" } = {}) => {
+  let encoding = whatwgEncoding.getBOMEncoding(buffer); // see https://github.com/whatwg/html/issues/1910
+
+  if (encoding === null && transportLayerEncodingLabel !== undefined) {
+    encoding = whatwgEncoding.labelToName(transportLayerEncodingLabel);
+  }
+
+  if (encoding === null) {
+    encoding = prescanMetaCharset(buffer);
+  }
+
+  if (encoding === null) {
+    encoding = defaultEncoding;
+  }
+
+  return encoding;
+};
+
+// https://html.spec.whatwg.org/multipage/syntax.html#prescan-a-byte-stream-to-determine-its-encoding
+function prescanMetaCharset(buffer) {
+  const l = Math.min(buffer.length, 1024);
+  for (let i = 0; i < l; i++) {
+    let c = buffer[i];
+    if (c === 0x3C) {
+      // "<"
+      const c1 = buffer[i + 1];
+      const c2 = buffer[i + 2];
+      const c3 = buffer[i + 3];
+      const c4 = buffer[i + 4];
+      const c5 = buffer[i + 5];
+      // !-- (comment start)
+      if (c1 === 0x21 && c2 === 0x2D && c3 === 0x2D) {
+        i += 4;
+        for (; i < l; i++) {
+          c = buffer[i];
+          const cMinus1 = buffer[i - 1];
+          const cMinus2 = buffer[i - 2];
+          // --> (comment end)
+          if (c === 0x3E && cMinus1 === 0x2D && cMinus2 === 0x2D) {
+            break;
+          }
+        }
+      } else if ((c1 === 0x4D || c1 === 0x6D) &&
+         (c2 === 0x45 || c2 === 0x65) &&
+         (c3 === 0x54 || c3 === 0x74) &&
+         (c4 === 0x41 || c4 === 0x61) &&
+         (isSpaceCharacter(c5) || c5 === 0x2F)) {
+        // "meta" + space or /
+        i += 6;
+        const attributeList = new Set();
+        let gotPragma = false;
+        let needPragma = null;
+        let charset = null;
+
+        let attrRes;
+        do {
+          attrRes = getAttribute(buffer, i, l);
+          if (attrRes.attr && !attributeList.has(attrRes.attr.name)) {
+            attributeList.add(attrRes.attr.name);
+            if (attrRes.attr.name === "http-equiv") {
+              gotPragma = attrRes.attr.value === "content-type";
+            } else if (attrRes.attr.name === "content" && !charset) {
+              charset = extractCharacterEncodingFromMeta(attrRes.attr.value);
+              if (charset !== null) {
+                needPragma = true;
+              }
+            } else if (attrRes.attr.name === "charset") {
+              charset = whatwgEncoding.labelToName(attrRes.attr.value);
+              needPragma = false;
+            }
+          }
+          i = attrRes.i;
+        } while (attrRes.attr);
+
+        if (needPragma === null) {
+          continue;
+        }
+        if (needPragma === true && gotPragma === false) {
+          continue;
+        }
+        if (charset === null) {
+          continue;
+        }
+
+        if (charset === "UTF-16LE" || charset === "UTF-16BE") {
+          charset = "UTF-8";
+        }
+        if (charset === "x-user-defined") {
+          charset = "windows-1252";
+        }
+
+        return charset;
+      } else if ((c1 >= 0x41 && c1 <= 0x5A) || (c1 >= 0x61 && c1 <= 0x7A)) {
+        // a-z or A-Z
+        for (i += 2; i < l; i++) {
+          c = buffer[i];
+          // space or >
+          if (isSpaceCharacter(c) || c === 0x3E) {
+            break;
+          }
+        }
+        let attrRes;
+        do {
+          attrRes = getAttribute(buffer, i, l);
+          i = attrRes.i;
+        } while (attrRes.attr);
+      } else if (c1 === 0x21 || c1 === 0x2F || c1 === 0x3F) {
+        // ! or / or ?
+        for (i += 2; i < l; i++) {
+          c = buffer[i];
+          // >
+          if (c === 0x3E) {
+            break;
+          }
+        }
+      }
+    }
+  }
+  return null;
+}
+
+// https://html.spec.whatwg.org/multipage/syntax.html#concept-get-attributes-when-sniffing
+function getAttribute(buffer, i, l) {
+  for (; i < l; i++) {
+    let c = buffer[i];
+    // space or /
+    if (isSpaceCharacter(c) || c === 0x2F) {
+      continue;
+    }
+    // ">"
+    if (c === 0x3E) {
+      break;
+    }
+    let name = "";
+    let value = "";
+    nameLoop:for (; i < l; i++) {
+      c = buffer[i];
+      // "="
+      if (c === 0x3D && name !== "") {
+        i++;
+        break;
+      }
+      // space
+      if (isSpaceCharacter(c)) {
+        for (i++; i < l; i++) {
+          c = buffer[i];
+          // space
+          if (isSpaceCharacter(c)) {
+            continue;
+          }
+          // not "="
+          if (c !== 0x3D) {
+            return { attr: { name, value }, i };
+          }
+
+          i++;
+          break nameLoop;
+        }
+        break;
+      }
+      // / or >
+      if (c === 0x2F || c === 0x3E) {
+        return { attr: { name, value }, i };
+      }
+      // A-Z
+      if (c >= 0x41 && c <= 0x5A) {
+        name += String.fromCharCode(c + 0x20); // lowercase
+      } else {
+        name += String.fromCharCode(c);
+      }
+    }
+    c = buffer[i];
+    // space
+    if (isSpaceCharacter(c)) {
+      for (i++; i < l; i++) {
+        c = buffer[i];
+        // space
+        if (isSpaceCharacter(c)) {
+          continue;
+        } else {
+          break;
+        }
+      }
+    }
+    // " or '
+    if (c === 0x22 || c === 0x27) {
+      const quote = c;
+      for (i++; i < l; i++) {
+        c = buffer[i];
+
+        if (c === quote) {
+          i++;
+          return { attr: { name, value }, i };
+        }
+
+        // A-Z
+        if (c >= 0x41 && c <= 0x5A) {
+          value += String.fromCharCode(c + 0x20); // lowercase
+        } else {
+          value += String.fromCharCode(c);
+        }
+      }
+    }
+
+    // >
+    if (c === 0x3E) {
+      return { attr: { name, value }, i };
+    }
+
+    // A-Z
+    if (c >= 0x41 && c <= 0x5A) {
+      value += String.fromCharCode(c + 0x20); // lowercase
+    } else {
+      value += String.fromCharCode(c);
+    }
+
+    for (i++; i < l; i++) {
+      c = buffer[i];
+
+      // space or >
+      if (isSpaceCharacter(c) || c === 0x3E) {
+        return { attr: { name, value }, i };
+      }
+
+      // A-Z
+      if (c >= 0x41 && c <= 0x5A) {
+        value += String.fromCharCode(c + 0x20); // lowercase
+      } else {
+        value += String.fromCharCode(c);
+      }
+    }
+  }
+  return { i };
+}
+
+function extractCharacterEncodingFromMeta(string) {
+  let position = 0;
+
+  while (true) {
+    const indexOfCharset = string.substring(position).search(/charset/i);
+
+    if (indexOfCharset === -1) {
+      return null;
+    }
+    let subPosition = position + indexOfCharset + "charset".length;
+
+    while (isSpaceCharacter(string[subPosition].charCodeAt(0))) {
+      ++subPosition;
+    }
+
+    if (string[subPosition] !== "=") {
+      position = subPosition - 1;
+      continue;
+    }
+
+    ++subPosition;
+
+    while (isSpaceCharacter(string[subPosition].charCodeAt(0))) {
+      ++subPosition;
+    }
+
+    position = subPosition;
+    break;
+  }
+
+  if (string[position] === "\"" || string[position] === "'") {
+    const nextIndex = string.indexOf(string[position], position + 1);
+
+    if (nextIndex !== -1) {
+      return whatwgEncoding.labelToName(string.substring(position + 1, nextIndex));
+    }
+
+    // It is an unmatched quotation mark
+    return null;
+  }
+
+  if (string.length === position + 1) {
+    return null;
+  }
+
+  const indexOfASCIIWhitespaceOrSemicolon = string.substring(position + 1).search(/\x09|\x0A|\x0C|\x0D|\x20|;/);
+  const end = indexOfASCIIWhitespaceOrSemicolon === -1 ?
+    string.length :
+    position + indexOfASCIIWhitespaceOrSemicolon + 1;
+
+  return whatwgEncoding.labelToName(string.substring(position, end));
+}
+
+function isSpaceCharacter(c) {
+  return c === 0x09 || c === 0x0A || c === 0x0C || c === 0x0D || c === 0x20;
+}