Add Chunk.isSlimeChunk to check if a chunk can spawn slimes

src/main/java/org/bukkit/craftbukkit/CraftChunk.java

@@ -3,6 +3,7 @@ package org.bukkit.craftbukkit;
 import java.lang.ref.WeakReference;
 import java.util.Arrays;
 
+import java.util.Random;
 import net.minecraft.server.*;
 
 import org.bukkit.Chunk;
@@ -129,6 +130,12 @@ public class CraftChunk implements Chunk {
         return getWorld().unloadChunk(getX(), getZ());
     }
 
+    @Override
+    public boolean isSlimeChunk() {
+        // 987234911L is deterimined in EntitySlime when seeing if a slime can spawn in a chunk
+        return getHandle().a(987234911L).nextInt(10) == 0;
+    }
+
     public boolean unload(boolean save) {
         return getWorld().unloadChunk(getX(), getZ(), save);
     }