Implement isCursed for new enchantments

By: Senmori <thesenmori@gmail.com>

paper-api/src/main/java/org/bukkit/enchantments/Enchantment.java

@@ -214,6 +214,15 @@ public abstract class Enchantment {
      */
     public abstract boolean isTreasure();
 
+    /**
+     * Checks if this enchantment is a cursed enchantment
+     * <br>
+     * Cursed enchantments are found the same way treasure enchantments are
+     *
+     * @return true if the enchantment is cursed
+     */
+    public abstract boolean isCursed();
+
     /**
      * Check if this enchantment conflicts with another enchantment.
      *