Convert image URLs in React to require calls

This allows Webpack to insert the proper image URL after builds steps like
adding a hash and so on. The path you supply to `require` is relative to the JS
source file, just like any other would be.

src/components/views/context_menus/GroupInviteTileContextMenu.js

@@ -79,7 +79,7 @@ export default class GroupInviteTileContextMenu extends React.Component {
     render() {
         return <div>
             <div className="mx_RoomTileContextMenu_leave" onClick={this._onClickReject} >
-                <img className="mx_RoomTileContextMenu_tag_icon" src="img/icon_context_delete.svg" width="15" height="15" />
+                <img className="mx_RoomTileContextMenu_tag_icon" src={require("../../../../res/img/icon_context_delete.svg")} width="15" height="15" />
                 { _t('Reject') }
             </div>
         </div>;