Increase Donkey / Mule Inventory to a Full Chest

Donkey and mules should have at least a full chest of storage inventory, since the whole idea of using real animals to transport items is that they can carry far more than a human being. I also think horses should get a small 9 slot inventory for basic supplies, and camels should get a double chest of inventory, since they can not be manually directed by a rider but only dragged. If these mobs had their inventory increased to a useful volume, players would actually regularly use them, both early game and late game, which is a good thing for gameplay.