stract: add update script

pkgs/by-name/st/stract/package.nix

@@ -2,6 +2,7 @@
   lib,
   stdenv,
   fetchFromGitHub,
+  unstableGitUpdater,
   fetchurl,
   rustPlatform,
   pkg-config,
@@ -58,6 +59,8 @@ rustPlatform.buildRustPackage {
     rm -rf target/${stdenv.hostPlatform.rust.cargoShortTarget}/release/build/
   '';
 
+  passthru.updateScript = unstableGitUpdater { };
+
   meta = {
     description = "Open source web search engine hosted at stract.com targeted towards tinkerers and developers.";
     homepage = "https://github.com/StractOrg/stract";