How to put a strikethrough on an out of stock variant (size) in the product page?

Question:
How to put a strikethrough on an out of stock variant (size) in the product page?

Product:
Wix editore, product page

What are you trying to achieve:
How to put a strikethrough on an out of stock variant (size) in the product page. FOr now I only have a gray out variant.