SDL2_sound: add update script

Signed-off-by: Marcin Serwin <marcin@serwin.dev>

pkgs/by-name/sd/SDL2_sound/package.nix

@@ -4,6 +4,7 @@
   fetchFromGitHub,
   cmake,
   SDL2,
+  nix-update-script,
 }:
 
 stdenv.mkDerivation (finalAttrs: {
@@ -33,6 +34,8 @@ stdenv.mkDerivation (finalAttrs: {
 
   buildInputs = [ SDL2 ];
 
+  passthru.updateScript = nix-update-script { };
+
   meta = {
     description = "SDL2 sound library";
     mainProgram = "playsound";