Subsonic/navidrome support

Hey, I've been looking for a Navidrome player for a while, but having one in emacs would be great.

https://github.com/isamert/empv.el has support, but I can only access 50 random songs in a completing read interface, and the look of your setup in listen.el looks like exactly what I'd want.

I don't know the first thing about implementing it myself in a pull request, so I humbly ask you if you'd be interested in having a go.

Thanks a lot!!