add whtaspp link shopify shareoption produict page
<a href="whatsapp://send?text=-------here write the text you want to send before the link------------------ https://------your domain-----{{ product.url }}{{ page.url }}{{ article.url }}" class="btn btn--small btn--share ">
<img src="https://url_of_the_uploaded_whatsapp_icon/filename.jpg" role="presentation" class="icon" style="width:18px; height:18px" title="share with whatsapp" alt="whatsapp_icon">
<span class="share-title" aria-hidden="true"> whatsapp</span>
</span>
</a>