fix(prejoin): Use localFlipX on prejoin screen

react/features/base/premeeting/components/web/Preview.js

 
 export type Props = {
 
+    /**
+     * Flag controlling whether the video should be flipped or not.
+     */
+    flipVideo: boolean,
+
     /**
      * Flag signaling the visibility of camera preview.
      */
  * @returns {ReactElement}
  */
 function Preview(props: Props) {
-    const { videoMuted, videoTrack } = props;
+    const { videoMuted, videoTrack, flipVideo } = props;
+    const className = flipVideo ? 'flipVideoX' : '';
 
     if (!videoMuted && videoTrack) {
         return (
             <div id = 'preview'>
                 <Video
-                    className = 'flipVideoX'
+                    className = { className }
                     videoTrack = {{ jitsiTrack: videoTrack }} />
             </div>
         );
  */
 function _mapStateToProps(state, ownProps) {
     return {
+        flipVideo: state['features/base/settings'].localFlipX,
         videoMuted: ownProps.videoTrack ? ownProps.videoMuted : state['features/base/media'].video.muted,
         videoTrack: ownProps.videoTrack || (getLocalVideoTrack(state['features/base/tracks']) || {}).jitsiTrack
     };