Added webpack.ProvidePlugin for most used imports

Removed imports of React, connect, PropTypes throughout
Removed the "React" in React.Component/PureComponent

app/javascript/gabsocial/features/video/index.js

@@ -1,5 +1,3 @@
-import React from 'react';
-import PropTypes from 'prop-types';
 import { defineMessages, injectIntl, FormattedMessage } from 'react-intl';
 import { fromJS, is } from 'immutable';
 import { throttle } from 'lodash';
@@ -87,7 +85,7 @@ export const getPointerPosition = (el, event) => {
 };
 
 export default @injectIntl
-class Video extends React.PureComponent {
+class Video extends PureComponent {
 
   static propTypes = {
     preview: PropTypes.string,