there are available app for whatsapp.
You can also check our app which supports WhatsApp, Messenger etc. App will send the url of the products page with the chat too.
It's easy to add a WhatsApp chat icon if you use SuperLemon. It's one of the best customer support apps in Shopify, with a very user-friendly interface. Now they have an updated version, where you get many more new features for SuperLemon at a faster pace.