Refactor: Avoid use folder for one file

Fix #3

modules/system/apps/steam.nix

@@ -0,0 +1,22 @@
+{ config, pkgs, lib, ... }:
+
+with lib;
+let
+  cfg = config.modules.system.apps.steam;
+in
+{
+  options.modules.system.apps.steam = {
+    enable = mkEnableOption ''
+      Enable steam with my custom configurations
+    '';
+  };
+  config = mkIf cfg.enable {
+    programs.steam = {
+      enable = true;
+      extraPackages = with pkgs; [ gamescope ];
+      extraCompatPackages = with pkgs; [ proton-ge-bin ];
+    };
+
+    hardware.steam-hardware.enable = true;
+  };
+}