Add Enchantment#isTreasure()Z

Determines if the enchantment is a treasure enchantment - only available via means other than the enchantment table.

src/main/java/org/bukkit/craftbukkit/enchantments/CraftEnchantment.java

@@ -54,6 +54,11 @@ public class CraftEnchantment extends Enchantment {
         }
     }
 
+    @Override
+    public boolean isTreasure() {
+        return target.e(); // PAIL: isTreasure
+    }
+
     @Override
     public boolean canEnchantItem(ItemStack item) {
         return target.canEnchant(CraftItemStack.asNMSCopy(item));