Add repology badge
Add repology badge

This is just to advertise that beets is available in distros. The badge links to a list of distro packages for beets and the current versions they have available, which is useful for users and contributors.

jackwilsdon/beets,beetbox/beets,shamangeorge/beets,SusannaMaria/beets,sampsyo/beets,ibmibmibm/beets,jackwilsdon/beets,shamangeorge/beets,jackwilsdon/beets,shamangeorge/beets,shamangeorge/beets,sampsyo/beets,SusannaMaria/beets,sampsyo/beets,beetbox/beets,ibmibmibm/beets,ibmibmibm/beets,SusannaMaria/beets,beetbox/beets,jackwilsdon/beets,beetbox/beets,sampsyo/beets,SusannaMaria/beets,ibmibmibm/beets