insertOrderedList: Implement swapping the list and a <div>

[hajimehoshi]

w3c.78 says

<div contenteditable>
  <ul>
    <li><div>^foo|</div>bar</li>
    <li>baz</li>
  </ul>
</div>

is expected to be changed into

<div contenteditable>
  <div>
    <ol>
      <li>^foo|</li>
    </ol>
  </div>
  bar<br>
  <ul>
    <li>baz</li>
  </ul>
</div>

.