Set customer email address for Back in Stock modal

gistfile1.txt

{% if customer.email %}
  <script>
    $(document).load(function() { // wait for app JS to load
      BISPopover.ready.then(function() {  // wait for Back in Stock to create the iframe
        var iframe = $('#BIS_frame').get(0); // find the iframe
      
        if (iframe) {
          $(iframe.contentDocument).find("#email_address").val('{{customer.email}}'); // set the email address field in the iframe
        }
      })
    })
  </script>
{% endif }