Update docs/storefront/cart-checkout/guide/add-to-cart-url.mdx

Co-authored-by: Valentin Dellangela <[email protected]>

docs/storefront/cart-checkout/guide/add-to-cart-url.mdx

@@ -36,7 +36,7 @@ Below is a table of common scenarios and example URLs.
 | Add product to cart and set coupon code                      |`https://{{domain}}/cart.php?action=add&product_id={{id}}&couponcode={{code}}`          |
 
  <Callout type="info">
-  It is required to have a product ID within the URL to add a coupon code.
+  It is required to have a product ID or a sku within the URL to add a coupon code.
  </Callout>
 
 Once constructed, a URL can be inserted directly as text or as an HTML link: