added WIP 'custom_dimension' to the API

src/main/java/carpet/fakes/MinecraftServerInterface.java

@@ -1,11 +1,16 @@
 package carpet.fakes;
 
+import net.minecraft.server.world.ServerWorld;
+import net.minecraft.util.registry.RegistryKey;
+import net.minecraft.world.World;
 import net.minecraft.world.level.storage.LevelStorage;
 
+import java.util.Map;
 import java.util.function.BooleanSupplier;
 
 public interface MinecraftServerInterface
 {
     void forceTick(BooleanSupplier sup);
     LevelStorage.Session getCMSession();
+    Map<RegistryKey<World>, ServerWorld> getCMWorlds();
 }