[Feature Request] Embed Video Metadata

[Brancliff]

Since this project uses YouTube-DLP, it would be super great to also feature the ability to embed the video's thumbnail and metadata into the videofile. It doesn't add on much to the filesize, so it could be enabled by default, with the option not to do it.

Once you get the user's video downloads, when it gets passed along to yt-dlp, it should be as easy as adding --embed-thumbnail --embed-metadata to the command. Possibly --embed-subs too, but then that gets into whether or not the user wants to only get officially-supported subs, or if the automatically-generated subs should be added as well