YT & YT Music non-album playlist download is not supported

[denyshon]

Describe the bug
YouTube and YouTube Music non-album playlist download is not supported.

Additional context
The cause is broken YouTubeMusicDL.download_playlist(). Playlist links are not parsed correctly.

[denyshon]

Adding priority-low since it's not a common use case. Also, that's a wontfix for now, since to fix the issue, a patch to python-youtube-music is needed, which seems to require the knowledge of the YT Music response format.