Allow a collapsible SotD section

[jyasskin]

If I edit a spec to turn the

<h2>Status of this document</h2>
Section contents

into

<details>
  <summary><h2>Status of this document</h2></summary>
  Section contents
</details>

it starts failing pubrules with There must be a status section that follows the abstract, labeled with an h2 element with content "Status of This Document". The Team maintains the status section of a document. Obviously there is a status section here; Specberus just doesn't know to look inside the <details> for it.

I'd like to do this for https://w3ctag.github.io/explainers/, where ideally people reading it would start their experience by looking at the document's actual content, and not the W3C's metadata.

[deniak]

A good number of pubrules' checks are related to the SotD which lists some important bits (stability of the document, IPR, process document, etc). Most web developers won't care about that section but it's not clear to me if we could/should make it less visible.

Also, having a <h2> in the summary can cause some alignment issues (see screenshot below). We could tweak the stylesheet but I'm not a big fan of that option. The alternative would be to not use a heading but it will make the section even less visible.

/cc @plehegar

[jyasskin]

The style problem, aside maybe from some margin collapsing, is fixed with

<details><summary style="list-style-position:outside">
 <h2 style="display:inline-block">...

Documents that want to do this could keep that style inline if folks don't think it belongs in the main stylesheet.

I think it's important that the information be there, but that most readers are skipping over this section anyway when they look at our documents.