title: Quill doesn't load content correctly
body: <p>I got an issue with Quill's <code>setContent</code> method. Everything works fine when I save the content but when I try to load it the attributes of my video/iframe tag are not being added. Do you have any idea why? (for images it works fine).</p>
  <p>Here is the content as JSON:
  <a href="https://i.stack.imgur.com/FVmc2.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/FVmc2.png" alt="enter image description here" /></a></p>
  <p>That is how I load the content:</p>
  <pre class="lang-js prettyprint-override"><code>quill.setContents(content, 'api');
  </code></pre>
  <p>And that is the output (as you can see, the image has the attributes, the iFrame does not)
  <a href="https://i.stack.imgur.com/swllq.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/swllq.png" alt="enter image description here" /></a></p>
  <p>FYI: I'm using this to resize the embeded videos: <a href="https://github.com/joaohenriiquee/quill-video-resize-module" rel="nofollow noreferrer">https://github.com/joaohenriiquee/quill-video-resize-module</a></p>