title: How to insert an iframe in a slack integration?
body: <p>The youtube slack integration inserts an image and when that image is clicked a youtube.com iframe gets inserted.</p>
  
  <p><a href="https://i.stack.imgur.com/KsStw.png" rel="noreferrer"><img src="https://i.stack.imgur.com/KsStw.png" alt="youtube iframe slack integration"></a></p>
  
  <p>How can my custom slack integration also insert an iframe? For example say I'd like to insert a codepen iframe?</p>