budgie-user-indicator-redux: add updateScript

pkgs/by-name/bu/budgie-user-indicator-redux/package.nix

@@ -10,6 +10,7 @@
   libpeas,
   meson,
   ninja,
+  nix-update-script,
   pkg-config,
   sassc,
   vala,
@@ -43,6 +44,10 @@ stdenv.mkDerivation (finalAttrs: {
     sassc
   ];
 
+  passthru = {
+    updateScript = nix-update-script { };
+  };
+
   meta = {
     description = "Manage your user session from the Budgie panel";
     homepage = "https://github.com/EbonJaeger/budgie-user-indicator-redux";