modules/steam: Add option to use the Jovian NixOS logo at launch

modules/steam/updater.nix

@@ -17,6 +17,7 @@ in
       splash = mkOption {
         type = types.enum [
           "steamos"
+          "jovian"
           "vendor"
         ];
         default = "steamos";
@@ -25,6 +26,8 @@ in
 
           When `steamos`, this will use the vendor-selected image, scaled appropriately.
 
+          When `jovian`, this will use the Jovian Experiments logo, scaled appropriately.
+
           When `vendor`, the vendor default will not be changed. This differs from `default` in that
           on systems other than the Steam Deck, the scaling may not be correct.
 
@@ -39,7 +42,12 @@ in
     {
       environment.etc."xdg/gamescope-session/environment" = {
         text = lib.mkAfter ''
-          jovian_updater_logo="$ui_background"
+          ${optionalString (cfg.updater.splash == "steamos") ''
+            jovian_updater_logo="$ui_background"
+          ''}
+          ${optionalString (cfg.updater.splash == "jovian") ''
+            jovian_updater_logo="${../../artwork/logo/splash.png}"
+          ''}
 
           ${pkgs.jovian-updater-logo-helper}/bin/jovian-updater-logo-helper "$jovian_updater_logo"