[FIX] web_editor: remove related videos at the end of youtube embeds

If a user embeds a youtube video on his website, he has no option to remove the
suggestion of related videos at the end of playback.
Since there is no good reason to have it, we disable the related videos in all
cases.

opw 1868380

addons/web_editor/static/src/js/widgets/widgets.js

@@ -820,6 +820,9 @@ var VideoDialog = Widget.extend({
             return {errorCode: 1};
         }
 
+        if (ytMatch) {
+            $video.attr('src', $video.attr('src') + '&rel=0');
+        }
         if (options.loop && (ytMatch || vimMatch)) {
             $video.attr('src', $video.attr('src') + '&loop=1');
         }