Is your feature request related to a problem? Please describe.
As of Minecraft 1.15(?), biomes are stored in 3D space. This should be exposed in the plugin and API.

Describe the solution you'd like
A direct 3D biome system should be implemented, that just hands off to the underlying implementation. On versions prior to 1.15, this would set the entire columns. On versions above, it'd set the 4x4x4 cube to that biome.

Some consideration would need to go into how we'd handle a case where a pattern sets multiple various biomes in the same "biome space" in a single edit.