Add bot icon to bot avatars and migrate to newer version of Font Awesome (#8484)

* Migrate to newer version of Font Awesome

* Add bot icon to bot avatars

app/javascript/mastodon/components/bot_icon.js

@@ -0,0 +1,23 @@
+import React from 'react';
+import ImmutablePropTypes from 'react-immutable-proptypes';
+import ImmutablePureComponent from 'react-immutable-pure-component';
+
+export default class BotIcon extends ImmutablePureComponent {
+
+  static propTypes = {
+    account: ImmutablePropTypes.map.isRequired,
+  };
+
+  render () {
+    const { account } = this.props;
+
+    if (account.get('bot')) {
+      return (
+        <i className='fa fa-fw fa-robot bot-icon' />
+      );
+    }
+
+    return '';
+  }
+
+}