Move Nix files back to the root of the project

modules/nixos/desktop/screenkey.nix

@@ -0,0 +1,25 @@
+{
+  config,
+  lib,
+  pkgs,
+  username,
+  ...
+}:
+
+with lib;
+
+{
+  options.nixosModules.screenkey.enable = mkEnableOption "Enable screenkey";
+
+  config = mkIf config.nixosModules.screenkey.enable {
+    environment.systemPackages = with pkgs; [ screenkey ];
+
+    home-manager.users.${username}.xdg.configFile."screenkey.json".text = builtins.toJSON {
+      key_mode = "composed";
+      mods_mode = "emacs";
+      persist = true;
+      size = "small";
+      timeout = 0.25;
+    };
+  };
+}