Minecraft wiki entry for Configured_structure_feature, associated text: The root tag
 type: The type of structure feature. Must be one of the types listed below.
 biomes: The biome tag that this structure is allowed to spawn in.
 adapt_noise: Optional. If true, terrain noise is adjusted so all pieces will generate on solid ground. Used for nether fossils, pillager outposts, strongholds, and villages. Defaults to false.
 spawn_overrides:[needs testing] Overrides the mobs that can spawn in this structure. Used for things like blaze and wither skeleton spawning in nether fortresses. Required, but can be an empty compound.
 config:
Configuration properties of this structure feature type, specified below.