overlays(srb2): add startupWMClass to desktop item

Fixes an issue with the application showing up as a question mark after
being launched in ironbar.

overlays/default.nix

@@ -7,6 +7,7 @@
     ./hyprlang.nix
     ./hyprlock.nix
     ./kitty.nix
+    ./srb2.nix
     ./zola.nix
   ];
 }

overlays/srb2.nix

@@ -0,0 +1,20 @@
+{
+  nixpkgs.overlays = [
+    (final: prev: {
+      srb2 = prev.srb2.overrideAttrs (oldAttrs: {
+        desktopItems = [
+          (prev.makeDesktopItem rec {
+            name = "Sonic Robo Blast 2";
+            exec = oldAttrs.pname;
+            icon = oldAttrs.pname;
+            comment = oldAttrs.meta.description;
+            desktopName = name;
+            genericName = name;
+            startupWMClass = ".srb2-wrapped";
+            categories = [ "Game" ];
+          })
+        ];
+      });
+    })
+  ];
+}