Natural Wither

the mod allows the wither to spawn naturally in the nether in any nether biome, anywhere in the nether dimension. it is through the use of a structure containing only a wither. the structure spawns roughly every 100 chunks, making it very rare, so gameplay is not heavily disrupted. the reason the changelog is empty is because this, (the 1st version), is  currently the complete version. I might one day add a config for which biomes but not right now.