Fix island.level config path

plugin/src/main/java/com/alttd/cometskyblock/island/Island.java

@@ -93,7 +93,7 @@ public class Island extends YamlConfiguration {
     }
 
     public int level() {
-        return getInt("island.id", 0);
+        return getInt("island.level", 0);
     }
 
     public void level(int id) {