title: Mark some content as uneditable inside Quilljs container
body: <p>Is it possible to mark some content inside a quill container as unmodifiable? For example, suppose the starting container div is:</p>
  
  <pre><code>&lt;div id="editor-container"&gt;
     &lt;h1&gt;This should not be editable.&lt;/h1&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>And my javascript is simply:</p>
  
  <pre><code>var quill = new Quill('#editor-container', {
    modules: {
      toolbar: [
        [{ header: [1, 2, false] }],
        ['bold', 'italic', 'underline'],
        ['image', 'code-block']
      ]
    },
    theme: 'snow'
  });
  </code></pre>
  
  <p>I tried setting the contenteditable attribute on the heading to false but that didn't help. The heading was still editable in the resulting Quill editor. I also tried adding a "readonly" attribute but that didn't work either.</p>
  
  <p>I have created the <a href="https://jsfiddle.net/thirteenfishes/k11ea10h/" rel="nofollow noreferrer">this jsfiddle</a> to show the readonly and contenteditable attempts.</p>
  
  <p>Any ideas on how to do this would be greatly appreciated!</p>