Add the details element as part of the disclosure pattern

[csarven]

https://www.w3.org/WAI/ARIA/apg/patterns/disclosure/ states:

a disclosure button and a section of content whose visibility is controlled by the button.

This seems to be a limitation considering the purpose that the details element serves. I suggest extending the text to include details element as part of the disclosure pattern, by perhaps also creating https://www.w3.org/WAI/ARIA/apg/patterns/disclosure/details

See also https://github.com/w3c/aria-practices/issues/2770