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

By: Senmori <thesenmori@gmail.com>

paper-api/src/main/java/org/bukkit/Chunk.java

@@ -123,4 +123,11 @@ public interface Chunk {
      * @return true if the chunk has unloaded successfully, otherwise false
      */
     boolean unload();
+
+    /**
+     * Checks if this chunk can spawn slimes without being a swamp biome.
+     *
+     * @return true if slimes are able to spawn in this chunk
+     */
+    boolean isSlimeChunk();
 }