New mole mob for mountain and plains biomes

While caving in either a plains or mountains/extreme mountains, you can find Mole tunnels which, as the name suggests, have been dug by the new Moles. The tunnels consist of various semiprecious materials that the moles salvage. Every tick there is a small chance that a mole will spawn in the tunnels, and if the player finds one they can feed it golden carrots, beetroot, fish or apples and the Mole will help the player mine by giving them haste and following them around. No mobs are hostile towards the Mole apart from zombies and withers. The Mole drops 1-2 string and occasionally a piece of dirt.