Added Steam in gaming

modules/userapps/gaming.nix

@@ -0,0 +1,19 @@
+{
+  config,
+  pkgs,
+  ...
+}: {
+  programs.steam = {
+    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
+    localNetworkGameTransfers.openFirewall = true; # Open ports in the firewall for Steam Local Network Game Transfers
+  };
+  nixpkgs.config.allowUnfreePredicate = pkg:
+    builtins.elem (lib.getName pkg) [
+      "steam"
+      "steam-original"
+      "steam-unwrapped"
+      "steam-run"
+    ];
+}