feat: steam and gamesession

hosts/battleship/configuration.nix

@@ -1,4 +1,8 @@
-{lib, ...}: {
+{
+  lib,
+  pkgs,
+  ...
+}: {
   imports = [
     ./hardware-configuration.nix
     ./gpu-configuration.nix
@@ -16,4 +20,12 @@
     hostName = lib.mkForce "figther";
     wireless.enable = lib.mkForce true;
   };
+
+  # Steam (cannot be [properly] installed just in one user)
+  programs.steam.enable = true;
+  programs.steam.gamescopeSession.enable = true;
+  programs.steam.extraCompatPackages = with pkgs; [
+    proton-ge-bin
+  ];
+
 }