update checkout when change zip code

Automatically update the checkout when the zip code is changed.

add_action('woocommerce_review_order_before_cart_contents', function (){
	 if ( is_checkout() ) { ?>
        <script type="text/javascript">
          jQuery('form.checkout').on('change', '#billing_postcode', function () {
            jQuery('body').trigger('update_checkout');
          });
        </script>
    <?php
	 }
});