MC_POST_NEW_ROOM and MC_POST_NEW_LEVEL should pass the room and level we're about to enter

[Foks256]

So instead of doing this:

mod:AddCallback(ModCallbacks.MC_POST_NEW_ROOM, function()
   local room = Game():GetRoom()

   if room:IsClear() then
      print("nice")
   end
end)

We could do something like this:

mod:AddCallback(ModCallbacks.MC_POST_NEW_ROOM, function(_, room)
   if room:IsClear() then
      print("nice")
   end
end)