Add two new mobs: the Zombie Bear and the Winter Zombie.

Add these mobs to Minecraft along with some small mechanics for them.

• The Zombie Bear will work similarly to the Zombie Camel, but will spawn only in snowy biomes. It will be able to carry two mobs on its back — a Stray and a Winter Zombie with a spear.

• The Winter Zombie will inflict the Mining Fatigue effect on the player when attacking.