title: How to add an attribute to a list item that is recorded in the Delta object?
body: <p>To implement a check-list feature with quill, I'm extending the ListItem class to add a &quot;check&quot; attribute. This is how I'm doing it.</p>
  <pre><code>class CheckListItem extends ListItem {
  
  static create(value) {
    let node = super.create()
    node.setAttribute('check', 'todo')
    return node;
  }
  
   ...
  } 
  CheckListItem.blotName = 'check'
  
  ...
  
  List.defaultChild = &quot;check&quot;
  List.allowedChildren = [CheckListItem]
  </code></pre>
  <p>When I inspect the element, I can see that the attribute has been added correctly to the <code>li</code> node. But it doesn't get recorded in the Delta object, so I cannot save the checklist state.</p>
  <p>How can I make my custom attribute show up the the Delta object?</p>