request: new policy profile for becoming an Mpris2 player

Created by: wdehoog

Can we have a new 'policy group' (or whatever it is called) to allow apps to register itself as an Mpris2 compatible player?

I have an app that plays music and when it registers itself as an Mpris2 player it can be controlled using the media controls on the indicator panel.

Right now my app is unconfined so it can register itself as an Mpris2 player. I think adding this new policy group would be a valuable feature for other apps as well.