Add Usenet option

[TobiasB91]

Is your feature request related to a problem? Please describe. I would like to use this single solution to manage my media server, but since I am not a torrent but a usenet user, I need to configure additional packages within nix.

Describe the solution you'd like Since the transmission module is already part of this module, an option for usenet users would be appreciated. I'm not opinionated on any particular downloader, but there are options like sabnzbd or nzbget

Describe alternatives you've considered

Additional context