Allow blacklisting media players

[KTibow]

I'd like to blacklist Nothing X which always has this

(plugin: MPRIS)

[andyholmes]

This has been a long standing problem with clients that forward media players that should be hidden, but I have no plans to implement an incoming allowlist/denylist at this time.

It's possible I might implement an outgoing denylist, but if it's not desirable to forward a media player that should be done on the exporting device, like notifications.