[Planned] Save tempo setting per playlist

[quzkat]

As title says, save tempo and maybe other sound effects/equalizer settings per playlist. But I'm mainly interested in tempo.

Use case: I have a playlist for podcasts which I always want to have at 1.5x or 2x, but other music related playlists should always be 1x. Currently it's annoying me to no end to always have to switch it when I change between listening to podcast and music.