Finishes the ActionCost implementation

src/main/java/net/knarcraft/blacksmith/manager/EconomyManager.java

@@ -151,6 +151,20 @@ public class EconomyManager {
         }
     }
 
+    /**
+     * Withdraws money from a player
+     *
+     * @param player <p>The player to withdraw from</p>
+     * @param monetaryCost <p>The cost to withdraw</p>
+     * @throws IllegalArgumentException <p>If a negative cost is given</p>
+     */
+    public static void withdraw(@NotNull Player player, double monetaryCost) {
+        if (monetaryCost < 0) {
+            throw new IllegalArgumentException("Cannot withdraw a negative amount");
+        }
+        economy.withdrawPlayer(player, monetaryCost);
+    }
+
     /**
      * Gets the cost of the item in the given player's main hand
      *