I redid the cli structure to group all the playlist commands under one common playlist parent command. I also implemented a clean up command to help people save disk space because SSDs are expensive right now.

For example:
music-syncer-kotlin -p path init -> music-syncer-kotlin playlist -p path init

This was a necessary step so I could implement the clean up command, which deletes audio and thumbnail files that are not used by any playlists in a container. A container is the folder holding all the databases.

Here’s everything I did, stolen from my commit message:

feature: add clean-container command
- refactor: add hasTrackInDatabase to the Playlist class
- refactor: move knownFinal{Audio,Thumbnail}Extension out of class and
	make it const
- refactor: nest all playlist commands as one subcommand
- refactor: make cli help text more helpful
- refactor: always print something to the console to let the user know
	that everything went well
- refactor: do not use PlaylistHolder, use
	currentContext.registerJvmCloseable to clean up playlist
- fix: when thumbnail is newly created, retag should silently fail