canvas: video preview thumbnails

[jronallo]

Several video players allow for preview thumbnails over the time rail
via a metadata WebVTT file that references thumbnail sprites with
media fragments. Is there any way to expose this kind of metadata
file on a canvas to where it is clear what the intended use of the
file is? Is this a service?

List of some players that support this already: https://github.com/jronallo/video_sprites#players

See an example canvas here: https://gist.github.com/jronallo/b455a5ddab2ce4b28d55c7708603f85a