Added steam and flatpak modules. Fixed steam with impermanence

nixos/modules/steam/default.nix

@@ -0,0 +1,29 @@
+{
+  pkgs,
+  lib,
+  config,
+  hwconfig,
+  ...
+}: let
+  cfg = config.kk.steam;
+in {
+  options.kk.steam = {
+    enable = lib.mkEnableOption "Enable steam";
+  };
+
+  config = lib.mkIf cfg.enable (
+    if hwconfig.useImpermanence
+    then {
+      kk.services.flatpak.enable = lib.mkForce true;
+      services.flatpak.packages = ["com.valvesoftware.Steam"];
+    }
+    else {
+      programs.steam = {
+        enable = !hwconfig.useImpermanence;
+        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
+      };
+    }
+  );
+}