[Sprint/QuietQuail](feat) Rich embed open in media modals #2162

Summary

Opening youtube videos in modals.

Testing

This has the potential to affect

My test plan (note gifs aren't working at present on sandboxes): Visit: https://feat-rich-embed-modals-2162.minds.io/richembedtest/

• Click through the content.
• Test in groups, comments and discovery>latest.
• Flip the feature flag via helm (any help, let me know).
• Refresh and check that everything still works

Try a variety of content.

src/app/common/components/rich-embed/rich-embed.scss

@@ -16,9 +16,6 @@ minds-rich-embed {
     left: 0;
     width: 100%;
     height: 100%;
-    @include m-theme() {
-      background-color: rgba(themed($m-black-always), 0.2);
-    }
 
     &:hover {
       background: transparent;