Do not load unnecessary script files (#4193)

app/javascript/packs/about.js

@@ -0,0 +1,24 @@
+import TimelineContainer from '../mastodon/containers/timeline_container';
+import React from 'react';
+import ReactDOM from 'react-dom';
+import loadPolyfills from '../mastodon/load_polyfills';
+import ready from '../mastodon/ready';
+
+require.context('../images/', true);
+
+function loaded() {
+  const mountNode = document.getElementById('mastodon-timeline');
+
+  if (mountNode !== null) {
+    const props = JSON.parse(mountNode.getAttribute('data-props'));
+    ReactDOM.render(<TimelineContainer {...props} />, mountNode);
+  }
+}
+
+function main() {
+  ready(loaded);
+}
+
+loadPolyfills().then(main).catch(error => {
+  console.error(error);
+});