This makes the hjem ghostty module more RFC42 compliant, as it can now
map nested attribute sets one level deep (as per Ghostty's configuration
format).
As my NixOS configuration kept growing, I noticed that I don't need
home-manager as much as I did before. A lot of what I need is just a way
to map nix attrsets to the program's respective configuration format,
which is something that I can now do myself, as my nix knowledge got
more extensive. After all of this, I decided to completely get rid of
home-manager, and switch to a simpler solution called hjem, which just
lets me write files to my home directory that are automatically
symlinked using `systemd-tmpfiles`.
This allows me to simplify my configuration, remove the separation
between NixOS and home-manager modules, and cut my eval times by quite a
lot (which allows for faster `nixos-rebuild switch`!).
