Index: frontend/node_modules/postcss-discard-overridden/README.md
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+# PostCSS Discard Overridden
+
+[PostCSS] plugin to discard overridden `@keyframes` or `@counter-style`.
+
+`@keyframes` or `@counter-style` will be overridden by those who share the same identifiers and appear later in stylesheets. So we can discard all of them except the last one. When defined inside a `@media` or `@supports` rule, `@keyframes` and `@counter-style` rules only override global rules in some of the client browsers so they need handled separately. This plugin has taken care of this and transforms the PostCss AST **safely**.
+
+[PostCSS]: https://github.com/postcss/postcss
+
+```css
+@-webkit-keyframes fade-in {
+  0% {
+    opacity: 0;
+  }
+  100% {
+    opacity: 0.8;
+  }
+}
+@keyframes fade-in {
+  0% {
+    opacity: 0;
+  }
+  100% {
+    opacity: 0.8;
+  }
+}
+@media (max-width: 500px) {
+  @-webkit-keyframes fade-in {
+    0% {
+      opacity: 0;
+    }
+    100% {
+      opacity: 1;
+    }
+  }
+  @keyframes fade-in {
+    0% {
+      opacity: 0;
+    }
+    100% {
+      opacity: 1;
+    }
+  }
+  @-webkit-keyframes fade-in {
+    0% {
+      opacity: 0;
+    }
+    100% {
+      opacity: 0.8;
+    }
+  }
+  @keyframes fade-in {
+    0% {
+      opacity: 0;
+    }
+    100% {
+      opacity: 0.8;
+    }
+  }
+  @supports (display: flex) {
+    @-webkit-keyframes fade-in {
+      0% {
+        opacity: 0;
+      }
+      100% {
+        opacity: 1;
+      }
+    }
+    @keyframes fade-in {
+      0% {
+        opacity: 0;
+      }
+      100% {
+        opacity: 1;
+      }
+    }
+  }
+}
+@-webkit-keyframes fade-in {
+  0% {
+    opacity: 0;
+  }
+  100% {
+    opacity: 1;
+  }
+}
+@keyframes fade-in {
+  0% {
+    opacity: 0;
+  }
+  100% {
+    opacity: 1;
+  }
+}
+```
+
+```css
+@media (max-width: 500px) {
+  @-webkit-keyframes fade-in {
+    0% {
+      opacity: 0;
+    }
+    100% {
+      opacity: 0.8;
+    }
+  }
+  @keyframes fade-in {
+    0% {
+      opacity: 0;
+    }
+    100% {
+      opacity: 0.8;
+    }
+  }
+  @supports (display: flex) {
+    @-webkit-keyframes fade-in {
+      0% {
+        opacity: 0;
+      }
+      100% {
+        opacity: 1;
+      }
+    }
+    @keyframes fade-in {
+      0% {
+        opacity: 0;
+      }
+      100% {
+        opacity: 1;
+      }
+    }
+  }
+}
+@-webkit-keyframes fade-in {
+  0% {
+    opacity: 0;
+  }
+  100% {
+    opacity: 1;
+  }
+}
+@keyframes fade-in {
+  0% {
+    opacity: 0;
+  }
+  100% {
+    opacity: 1;
+  }
+}
+```
+
+## Usage
+
+See the [PostCSS documentation](https://github.com/postcss/postcss#usage) for
+examples for your environment.
+
+## Contributors
+
+See [CONTRIBUTORS.md](https://github.com/cssnano/cssnano/blob/master/CONTRIBUTORS.md).