Added 1.21 Support
Added 3 new advancements:
So Below... -> Get below y=0 in the Nether Breaking Bad -> Get to the Nether Roof at y=320
There is a secret advancement.
Build Height limit is now 511 (576 blocks total)
Dropped support for related mods (as it can break the mod) and added failsafe for future snapshots.
Initial Release
