Add a 'domain' option to the NixOS module and JSON config that
controls the domain suffix used for internal DNS names. Defaults to
'hyprspace' for backward compatibility. Supports multi-label domains
(e.g. 'vpn.internal').
Co-authored-by: Max <max@privatevoid.net>
* README: document basic build/setup steps
* document dev setup and how the config schema works
* set up for use with direnv
* mention direnv in the dev setup docs
* README: mention developer docs
* provide some contributor infos
