front-addon.html

<div class="plugin">
  <h1>Demo Extension</h1>
  <button class="assign-self">Take lead</button>

  <button class="auto-reply">Auto Reply</button>
    
  <div class="contact-info">
      <h2>Contact Info</h2>
      <span></span>
  </div>
    
  <div class="message-info">
      <h2>Message extract</h2>
      <span></span>
  </div>
</div>

<div class="front">
    <iframe id="front" height="100%" width="100%" seamless frameborder="0" marginheight="0" marginwidth="0" scrolling="no" src="https://app.frontapp.com"></iframe>
</div>