video cover support

[foxjaw]

Some videos also contain cover art. Sometimes as a 2nd video stream:

Stream #0:2[0x0]: Video: png, rgb24(pc, gbr/unknown/unknown), 1280x720, 90k tbr, 90k tbn (attached pic)

& sometimes as an webp image attachment

Stream #0:2: Attachment: none
    Metadata:
      filename        : cover.webp
      mimetype        : image/webp

of video downloaded from yt-dlp with --embed-thumbnail flag. Not sure how to pull this off in config file. Probably has to do something with ffprobe.