[request]Single Stage support multiple Kill MythicMobs Objective

[hkkongou]

So far the mythicmobsquestsmodule seems only support single stage detect single mythicmob kill count. This will force quest developers to make kill count into several stages, this will make players feel inconvenient for killing mobs.
If a stage can support multiple type of kill mythicmobs objective, players can kill different kind of mobs at the same stage and finish quest easily, they would not need to wait for new stage to kill other type of mob.