feat(pocket-base): add purchasable biome changes

README.md

@@ -30,6 +30,7 @@ The plugin JAR is written to `build/libs/`.
 /basesettings upgrade
 /basesettings pocket upgrade
 /basesettings pocket mobs <enable|disable>
+/basesettings pocket type <void|nether|overworld> <subtype>
 /basesettings visitors <allowed|blocked>
 /basesettings navigation <enable|disable>
 /basesettings flight <enable|disable>
@@ -46,6 +47,8 @@ After 250 Survival-mode block placements anywhere by default, the spawnable over
 
 Base IV owners can purchase and expand a persistent Pocket Base with `/basesettings pocket upgrade`. Activating a complete diamond-block portal frame inside the normal base with flint and steel opens one public entrance to the owner's grass platform in a private void world. The owner can move the return portal by building and igniting another complete frame inside the unlocked Pocket Base boundary; only the newly activated return portal remains functional. Natural hostile and passive mob spawning is disabled by default and can be controlled by the owner with `/basesettings pocket mobs <enable|disable>`.
 
+Owners can change biome metadata without altering Pocket Base blocks, entities, inventories, or portals by using `/basesettings pocket type <void|nether|overworld> <subtype>`. Void uses `the_void`; Nether and Overworld accept their compatible vanilla biome names, such as `crimson_forest` or `plains`. Each change defaults to 16 netherite blocks, is configurable, and affects applicable natural mob selection when spawning is enabled. The Pocket Base remains a void-generated normal-environment world; dimension-specific mechanics do not change.
+
 ## Administration
 
 The `spigotbase.admin` permission is granted to server operators by default. `/homeadmin` aliases `/baseadmin`.