Added steam common module

modules/common/steam.nix

@@ -0,0 +1,12 @@
+{
+  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
+  };
+}