title: quill classes in quill.root.innerHTML is not working
body: <p>I'm using quill in angular4 and I have a problem. I want to save a quill text in the database and I'm using <code>quill.root.innerHTML</code> to save it. but when I want to show the text, it only applies the tags that are generated, like  or  but the classes like <code>class="ql-direction-rtl ql-align-center"</code> or <code>class="ql-size-large"</code> are not applying on the text.
   here are codes: </p>
  
  <p>html:</p>
  
  <pre><code>&lt;select class="ql-align"&gt;
                  &lt;option selected=""&gt;&lt;/option&gt;
                  &lt;option value="center"&gt;&lt;/option&gt;
                  &lt;option value="right"&gt;&lt;/option&gt;
                  &lt;option value="justify"&gt;&lt;/option&gt;
                &lt;/select&gt;
  </code></pre>
  
  <p>ts</p>
  
  <pre><code>//use to get text from db
  this.quill.root.innerHTML = mail.mail.rows[0].content;
  </code></pre>