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/containers/compose_container.js

@@ -0,0 +1,39 @@
+import React from 'react';
+import { Provider } from 'react-redux';
+import PropTypes from 'prop-types';
+import configureStore from '../store/configureStore';
+import { hydrateStore } from '../actions/store';
+import { IntlProvider, addLocaleData } from 'react-intl';
+import { getLocale } from '../locales';
+import Compose from '../features/standalone/compose';
+
+const { localeData, messages } = getLocale();
+addLocaleData(localeData);
+
+const store = configureStore();
+const initialStateContainer = document.getElementById('initial-state');
+
+if (initialStateContainer !== null) {
+  const initialState = JSON.parse(initialStateContainer.textContent);
+  store.dispatch(hydrateStore(initialState));
+}
+
+export default class TimelineContainer extends React.PureComponent {
+
+  static propTypes = {
+    locale: PropTypes.string.isRequired,
+  };
+
+  render () {
+    const { locale } = this.props;
+
+    return (
+      <IntlProvider locale={locale} messages={messages}>
+        <Provider store={store}>
+          <Compose />
+        </Provider>
+      </IntlProvider>
+    );
+  }
+
+}