Add youtube shorts url rule and fix youtube video embedding

[twinkarma]

• [x] Support youtube shorts url
• [x] Fixed embedding for normal youtube videos
• [x] Show "The Assistant could not display this video content." message in place for youtube shorts,
  • Translations are in this PR https://github.com/AFP-Medialab/InVID-Translations/pull/86
• Youtubeshorts Services linked by the assistant
  • [x] Video analysis - Disabled - We cannot extract an video ID from the submitted URL. Please note also that Facebook does not allow us to process videos from Users or Groups. Support for ytshorts is on Olga's list of todos but no clear timeframe.
  • [x] Keyframe - Works
  • [x] Thumbnail - Disabled - Runs but no thumbnail generated, Denis' team will be looking into this.
  • [x] Video rights - Disabled- Unknown error occurred, service no longer maintained.

[twinkarma]

This is what embedding looks like with youtube shorts. Should we put some placeholder graphics in?

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• Add message to effect of "Youtube shorts only partially supported"
• Simplify text about youtube shorts video embeddeding

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Thanks for the review @rosannamilner !