New overworld biome: decayed forest

Add a biome in the overworld known as the Decayed forests. In this biome, hostile mobs can always spawn at any light level, except on peaceful difficulty. All villages are either abandoned, or filled with zombie villagers. Zombie villagers cannot be cured in this biome. Also, undead mobs get a slight damage health and speed buff. All the wood here is known as rotted wood and the leaves drop poisonous apples, decayed saplings, and withered sticks. Tools crafted with withered sticks have a disadvantage where when used, the user loses an extra half a heart when hit, and the tool also has a 1% chance to give you 5 seconds of Poison I and a 0.1% for 10 seconds, 0.1% chance for 5 seconds withering, and 0.01% chance for 10 seconds. Upon breaking a withered tool, the player gets Instant Damage II effects. If there is no light, a zombie has a 30% chance to spawn on your chunk every 5 seconds, having light near you decreases it to 10%, and lighting the entire chunk gives a 5% chance. This addition may seem like a complete waste of time that no one will ever use, but that is where this next part is useful. In the decayed forest, there is a 30% chance you will find a necromanced graveyard. This is a structure with unbelievable hostile mob spawn rates, but there's a 50% chance to find an altar in this graveyard. These altars are like the blacksmiths of the decayed forest, they give amazing loot, well worth the time it took to get there and get the loot.You could find anything good there.