treewide: Add passthru.updateScript to gnome pkgs

`updateScript` lets us update packages automatically.
For packages that are hosted on the gnome mirror it's very easy to add
that. Inspired by https://github.com/NixOS/nixpkgs/issues/36150

pkgs/development/tools/documentation/gnome-doc-utils/default.nix

@@ -1,12 +1,14 @@
-{fetchurl, pkgconfig, libxml2Python, libxslt, intltool
+{ stdenv, fetchurl, pkgconfig, libxml2Python, libxslt, intltool, gnome3
 , python2Packages }:
 
-python2Packages.buildPythonApplication {
-  name = "gnome-doc-utils-0.20.10";
+python2Packages.buildPythonApplication rec {
+  pname = "gnome-doc-utils";
+  version = "0.20.10";
+
   format = "other";
 
   src = fetchurl {
-    url = mirror://gnome/sources/gnome-doc-utils/0.20/gnome-doc-utils-0.20.10.tar.xz;
+    url = "mirror://gnome/sources/${pname}/${stdenv.lib.versions.majorMinor version}/${pname}-${version}.tar.xz";
     sha256 = "19n4x25ndzngaciiyd8dd6s2mf9gv6nv3wv27ggns2smm7zkj1nb";
   };
 
@@ -20,4 +22,17 @@ python2Packages.buildPythonApplication {
   '';
 
   propagatedBuildInputs = [ libxml2Python ];
+
+  passthru = {
+    updateScript = gnome3.updateScript {
+      packageName = pname;
+    };
+  };
+
+  meta = with stdenv.lib; {
+    description = "Collection of documentation utilities for the Gnome project";
+    homepage = https://gitlab.gnome.org/GNOME/gnome-doc-utils;
+    license = with licenses; [ gpl2Plus lgpl2Plus ];
+    platforms = platforms.all;
+  };
 }