Install on nixOs via flake instructions

[andycandy-dev]

In order to use swhkd package on nixOs:

1. requires Fix permission groups #325
2. I've added a packages output to the flake.nix file andycandy-dev@8a15e7a
   not as clean as it could have been but it works.
3. above flake provides two packages, I had to use swhkd-no-rfkill as of [fix] remove rfkill switch support #254 conversation - otherwise running swhkd nuked my wifi.
4. followed directions Latest changes to make swhkd work in Arch terminal #285 (comment) , which references Improve The Security Model #270 for setuid on my configuration.nix

{ config, lib, pkgs, inputs, ... }:
let
  swhkdPkg = inputs.swhkd.packages.x86_64-linux.swhkd-no-rfkill;
in
{
  security.wrappers.swhkd = {
    owner = "root";
    group = "root";
    setuid = true;
    source = "${swhkdPkg}/bin/swhkd";
  };
} 

5. setup userspace systemd with home-manager

{ config, lib, pkgs, inputs, ... }:
let
  username = config.home.username;
  swhkdPkg = inputs.swhkd.packages.x86_64-linux.swhkd-no-rfkill;
  swhks-launcher = pkgs.writeShellScript "swhks-launcher" ''
    ${pkgs.killall}/bin/killall swhks swhkd 2>/dev/null || true
    ${swhkdPkg}/bin/swhks &
    sleep 0.5
    /run/wrappers/bin/swhkd -c /home/${username}/.config/swhkd/swhkdrc
  '';
in
{
  xdg.configFile."swhkd/swhkdrc".source = config.lib.file.mkOutOfStoreSymlink "${config.home.homeDirectory}/nixos-dots/home/swhkd/swhkdrc"; 

  systemd.user.services.swhkd = {
    Unit.Description = "Simple Wayland HotKey Server";
    Unit.After = [ "graphical-session.target" ];
    Service = {
      ExecStart = "${swhks-launcher}";
      ExecReload = "${pkgs.coreutils}/bin/kill -HUP $MAINPID";
      Restart = "on-failure";
      KillMode = "mixed";
    };
    Install.WantedBy = [ "graphical-session.target" ];
  };
}