util: add traceback function that i stole

https://discord.com/channels/805969743466332191/827848307480461313/1120318388540022794

it was in a fucking shitpost channel
thanks again @dragekk this is probably the fifth thing i've stolen from
you

util.lua

@@ -204,4 +204,8 @@ local function recurseModelGroup(group)
 end
 util.recurseModelGroup=recurseModelGroup
 
+function util.traceback()
+    return ({pcall(function() error("", 4) end)})[2]:match("stack traceback:.+$")
+end
+
 return util