h2m converter fails to convert some <dl> elements

[wbamberg]

I'm not exactly sure of the problem, but the h2m converter can't convert certain <dl> elements. In particular this seems to happen when a <dd> immediately contains another list element or pre block.

For example, the following will not be converted:

<dl>
 <dt>an item</dt>
 <dd>
  <ul>
    <li>with a list</li>
  </ul>
 </dd>
</dl>

<dl>
 <dt>an item</dt>
 <dd>
  <pre>
    a pre block
  </pre>
 </dd>
</dl>

The following will be converted:

<dl>
 <dt>an item</dt>
 <dd>A definition.
  <ul>
    <li>with a list</li>
  </ul>
 </dd>
</dl>

<dl>
 <dt>an item</dt>
 <dd>A definition.
  <pre>
    a pre block
  </pre>
 </dd>
</dl>

These are not very common, but they don't seem invalid to me. Real-world examples:

https://developer.mozilla.org/en-US/docs/Web/CSS/@page/size
https://developer.mozilla.org/en-US/docs/Web/CSS/basic-shape
https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Fonts
https://developer.mozilla.org/en-US/docs/Web/CSS/url()
https://developer.mozilla.org/en-US/docs/Web/CSS/visibility

[wbamberg]

But also! Please see mdn/content#7309 in which we might decide we don't care about supporting <dd> elements that start with not-text.