mpris-proxy needs to be started for bluetooth headset controls to work

Describe your issue

What's the expected behaviour?

Bluetooth headset buttons should control music

What's the current behaviour?

Bluetooth headset buttons do not control music

How to reproduce your issue?

Connect bluetooth headphones, start a music player like lollypop, and try to use headset buttons to play/pause/skip

What device are you using?

pinephone ubports CE

On what postmarketOS version did you encounter the issue?

• edge (master branch)
• stable (v20.05 branch)

On what environment did you encounter the issue?

Phone environments

• Phosh
• Plasma Mobile
• Sxmo

Other

• No environment
• GNOME
• KDE Plasma
• Kodi
• MATE
• Shelli
• Sway
• Weston
• Xfce4
• fbkeyboard
• i3wm

How did you get postmarketOS image?

• from https://images.postmarketos.org
• I built it using pmbootstrap
• It was preinstalled on my device

What's the build date of the image? (in yyyy-mm-dd format)

Additional information