Create a product page theme block with a text input field where customers can enter a reference/order code before adding to cart. The input should:
- Have a label like "Reference Code" with optional helper text (customizable in theme editor settings)
- Store the entered value as a line item property so it appears on the order
- Include basic validation to ensure the field is filled in before the customer can add to cart (optional toggle in settings)
- Be styled to match the theme's existing form inputs
- Have settings in the theme editor for: label text, placeholder text, helper/instruction text, and whether the field is required
