feat(nixos): some moves to nixos server

nixos/system/games/default.nix

@@ -0,0 +1,22 @@
+{
+  flake,
+  self,
+  inputs,
+  system,
+  ...
+}: let
+  # Use folder name as name of this system
+  name = builtins.baseNameOf ./.;
+
+in self.lib.nixpkgs-lib.nixosSystem {
+  pkgs = import inputs.nixpkgs {
+    inherit system;
+    overlays = [ self.overlays.default ];
+    config.allowUnfreePredicate = pkg:
+      builtins.elem (inputs.nixpkgs.lib.getName pkg) [ "steamcmd" "steam-unwrapped" ];
+  };
+  modules = [
+    { networking.hostName = name; }
+    (import ./${name}.nix { inherit flake self inputs; })
+  ];
+}