restructure desktop with option config wrappers

modules/desktop/gaming/default.nix

@@ -0,0 +1,9 @@
+{
+  pkgs,
+  config,
+  lib,
+  ...
+}: {
+  imports = [
+  ];
+}

modules/desktop/greetd/default.nix

@@ -6,7 +6,7 @@
 }: let
   cfg = config.desktop.greetd;
 in {
-  options.desktop.hypr = {
+  options.desktop.greetd = {
     enable = lib.mkEnableOption "enable greetd with tuigreet";
   };