POST this JSON to <span class="origin"></span>/submit

<pre>
{
  "email": "your email",
  "secret": "your secret",
  "url": "<span class="origin"></span>/demo",
  "answer": "anything you want"
}
</pre>

<script type="module">
for (const el of document.querySelectorAll(".origin")) {
  el.innerHTML = window.location.origin;
}
</script>