<p> elements wrapped around <summary> elements producing invalid html5 (2.9.2.1)

[poppadum]

When converting the following markdown to html:

<details>
<summary>Show me:</summary>
details para 1

details para 2
</details>

produces:

<details>
<p><summary>Show me:</summary>details para 1</p>
details para 2
</details>

which is not valid html5. The <summary> element must be the first child of a <details> element (see the html5 spec)

I would expect the output to be

<details>
<summary>Show me:</summary>
<p>details para 1</p>
<p>details para 2</p>
</details>

This looks closely related to #3694

[tarleb]

As a work-around, stop pandoc from adding additional <p> tags by marking summary as a raw HTML block:

<details>
```{=html}
<summary>Show me:</summary>
```
details para 1

details para 2
</details>

[jgm]

fixed. Note that pandoc's parsing scheme will require a blank line after details para 2 if you want it to be treated as a paragraph, and not "plain inline content."