Completely overhauled the formatting system. Now uses full variable
names like {title} or {TITLE}. Added extra options for VLC since VLC
apparently uses a bunch of custom metadata types.
Also changed some things in the JSON representation of the song. It
should now contain all info that is available.
Fixed progress bar jumping around. The progress bar now smoothly moves
using the frame time and gradually speeds up or slows down if it is
behind/ahead of the actual song position.
Because this release changed a bunch of things there's a chance that something broke,
if that's the case you can always use the previous release and create an issue on gitea.