runelite: add updateScript

pkgs/games/runelite/default.nix

@@ -5,6 +5,7 @@
 , maven
 , jre
 , xorg
+, gitUpdater
 }:
 
 maven.buildMavenPackage rec {
@@ -45,6 +46,8 @@ maven.buildMavenPackage rec {
       --add-flags "-jar $out/share/RuneLite.jar"
   '';
 
+  passthru.updateScript = gitUpdater { };
+
   meta = {
     description = "Open source Old School RuneScape client";
     homepage = "https://runelite.net/";