feishin: add update script

pkgs/by-name/fe/feishin/package.nix

@@ -12,6 +12,7 @@
   darwin,
   copyDesktopItems,
   makeDesktopItem,
+  nix-update-script,
 }:
 let
   pname = "feishin";
@@ -147,6 +148,8 @@ buildNpmPackage {
     })
   ];
 
+  passthru.updateScript = nix-update-script { };
+
   meta = {
     description = "Full-featured Jellyfin, Navidrome, and OpenSubsonic Compatible Music Player";
     homepage = "https://github.com/jeffvli/feishin";