docs: mention group service registration
docs: mention group service registration

A few minor tweaks and cleanups as well.

hashicorp/nomad,hashicorp/nomad,dvusboy/nomad,burdandrei/nomad,hashicorp/nomad,dvusboy/nomad,burdandrei/nomad,dvusboy/nomad,dvusboy/nomad,burdandrei/nomad,burdandrei/nomad,burdandrei/nomad,hashicorp/nomad,dvusboy/nomad,dvusboy/nomad,hashicorp/nomad,hashicorp/nomad,dvusboy/nomad,burdandrei/nomad,burdandrei/nomad