gtm-tag-toastr.html

<link href="//cdnjs.cloudflare.com/ajax/libs/toastr.js/latest/css/toastr.min.css" rel="stylesheet"/>
<script>
(function() {
  var gtm = window.google_tag_manager[{{Container ID}}];
  var el = document.createElement('script');
  el.async = true;
  el.src = 'https://cdnjs.cloudflare.com/ajax/libs/toastr.js/latest/js/toastr.min.js';
  el.addEventListener('load', function() {
    gtm.onHtmlSuccess({{HTML ID}});
  });
  document.head.appendChild(el);
})();
</script>