Generate thumbnails for showcase materials
The previews for the videos in the community showcase panel appear black on Safari 13.1. (webm support is flaky in old versions of Safari, but mp4 previews also appear black)
The video previews are jank and need to be replaced with a proper thumbnail thing. They're literally just
<video> tags with some attributes set so they don't load more than the initial thumbnail. Chrome and Firefox display the first frame of the video when you do this. Unfortunately Safari does not. (I knew this was the case on mobile, but apparently this is also true on desktop.)
What we should actually be doing is extracting the first frame of the video using ffmpeg or whatever, and saving that as a separate linked asset.
Deleting a branch is permanent. It CANNOT be undone. Continue?