Tree climbing

Player should climb trees if not holding anything in hand. Done by crouching to a tree & jumping on it. Climbing them bare-hand, however, should also deplete hunger, and only possible if player is wearing leather, chainmail, or no armor. If player is too hungry or equips an item, player will fall. Allows trees to be taller in design, interesting to climb to each branch, and let/encourage players to cut them from the top-down.