to add Structures:

1. add the NBT to "resources/data/abandoned-world/structures/ancient_pyramid.nbt"
2. add or duplicate the has_Structure file in: "resources/data/abandoned-world/tags/worldgen/biome/has_structure"
3. add or duplicate the structure file in: "resources/data/abandoned-world/worldgen/structure"
4. add or duplicate the structure_set file in: "resources/data/abandoned-world/worldgen/structure_set"
5. add or duplicate the template_pool directory in: "resources/data/abandoned-world/worldgen/template_pool"
6. add or change the start_pool file in: "resources/data/abandoned-world/worldgen/template_pool"
