Replace to shakapacker from webpacker

app/javascript/about.js

@@ -0,0 +1,26 @@
+import 'mastodon/public-path';
+import loadPolyfills from 'mastodon/load_polyfills';
+import { start } from 'mastodon/common';
+
+start();
+
+function loaded() {
+  const TimelineContainer = require('mastodon/containers/timeline_container').default;
+  const React             = require('react');
+  const ReactDOM          = require('react-dom');
+  const mountNode         = document.getElementById('mastodon-timeline');
+
+  if (mountNode !== null) {
+    const props = JSON.parse(mountNode.getAttribute('data-props'));
+    ReactDOM.render(<TimelineContainer {...props} />, mountNode);
+  }
+}
+
+function main() {
+  const ready = require('mastodon/ready').default;
+  ready(loaded);
+}
+
+loadPolyfills().then(main).catch(error => {
+  console.error(error);
+});