add proton-ge to steam by default

share/gaming/default.nix

@@ -1,4 +1,4 @@
-{ lib, config, ... }:
+{ lib, config, pkgs, ... }:
 let
   cfg = config.share.gaming;
 in
@@ -16,7 +16,7 @@ in
       remotePlay.openFirewall = true;
       # Open ports in the firewall for Source Dedicated Server
       dedicatedServer.openFirewall = true;
-
+      extraCompatPackages = [ pkgs.proton-ge-bin];
       gamescopeSession = {
         enable = true;
         args = [