System76 Serval WS Configuration

[nickpdemarco]

https://github.com/NixOS/nixos-hardware/tree/master/system76 doesn't seem to contain a configuration for Serval WS.

I'd be happy to take on the work to write this configuration, but I'd likely need a mentor. I just purchased a Serval WS device and want to get NixOS running and stable, but I'm having some battery life issues I hope to address with a standard config from this repository.