nixos-shell: add updateScript

pkgs/by-name/ni/nixos-shell/package.nix

@@ -5,6 +5,7 @@
   jq,
   fetchFromGitHub,
   makeWrapper,
+  nix-update-script,
 }:
 
 stdenv.mkDerivation (finalAttrs: {
@@ -32,6 +33,8 @@ stdenv.mkDerivation (finalAttrs: {
 
   installFlags = [ "PREFIX=${placeholder "out"}" ];
 
+  passthru.updateScript = nix-update-script { };
+
   meta = {
     description = "Spawns lightweight nixos vms in a shell";
     inherit (finalAttrs.src.meta) homepage;