return GameObject in emmylua

obj/Area.lua

@@ -49,6 +49,7 @@ end
 ---@param x number|nil horizontal position
 ---@param y number|nil vertical position
 ---@param opts table|nil additional arguments
+---@return GameObject
 function Area:addGameObject(game_object_type, x, y, opts)
     local game_object = _G[game_object_type](self, x or 0, y or 0, opts or {})
     table.insert(self.game_objects, game_object)