join murmur (mumble server) automatically

[zsawyer]

@magneticflux- hints at the possibility to have the client automatically join the associated murmur.

This would work by means of using the mumble:// URI but would also require some server side mod to tell the client which URI.

1. It would be ideal to hook into whatever is provided by https://github.com/magneticflux-/fabric-mumblelink-mod at first.
2. Then we would probably need to figure out how to provide this for forge based servers.