added steam EpicGames and some other launchers for playing wideo games

nixos/hosts/usconfig/models/gamemode.nix

@@ -0,0 +1,17 @@
+{pkgs, ...}: {
+  programs.steam.enable = true;
+  programs.steam.gamescopeSession.enable = true;
+  programs.gamemode.enable = true;
+
+  environment.systemPackages = with pkgs; [
+    mangohud
+    protonup
+    bottles
+    heroic
+  ];
+
+  environment.sessionVariables = {
+    STEAM_EXTRA_COMPAT_TOOLS_PATHS =
+      "\${HOME}/.steam/root/compatibilitytools.d";
+  };
+}