add gamescope to steam and gamemode

modules/graphical/gamemode.nix

@@ -0,0 +1,11 @@
+{ config, lib, pkgs, ... }:
+
+{
+  programs.gamemode = {
+    enable = true;
+    settings.custom = {
+      start = "${pkgs.libnotify}/bin/notify-send 'GameMode started'";
+      end = "${pkgs.libnotify}/bin/notify-send 'GameMode ended'";
+    };
+  };
+}

modules/graphical/shared.nix

@@ -10,6 +10,7 @@ in
     enable = true;
     remotePlay.openFirewall = true; # Open ports in the firewall for Steam Remote Play
     dedicatedServer.openFirewall = true; # Open ports in the firewall for Source Dedicated Server
+    gamescopeSession.enable = true;
   };
 
   programs.kdeconnect.enable = true;