Add protocol handler. Handle follow intents (#4511)

* Add protocol handler. Handle follow intents

* Add share intent

* Improve code in intents controller

* Adjust share form CSS

app/javascript/mastodon/features/standalone/compose/index.js

@@ -0,0 +1,18 @@
+import React from 'react';
+import ComposeFormContainer from '../../compose/containers/compose_form_container';
+import NotificationsContainer from '../../ui/containers/notifications_container';
+import LoadingBarContainer from '../../ui/containers/loading_bar_container';
+
+export default class Compose extends React.PureComponent {
+
+  render () {
+    return (
+      <div>
+        <ComposeFormContainer />
+        <NotificationsContainer />
+        <LoadingBarContainer className='loading-bar' />
+      </div>
+    );
+  }
+
+}