Supports <details> using Admonitions mechanism

[sighingnow]

It would be great to have something like <details> of HTML in the furo theme:

.. details::

    xxxxxxx

and which will be rendered as

<details>
xxxxxxxx
</details>

[sighingnow]

See also: https://www.w3schools.com/tags/tag_details.asp

[sighingnow]

If such proposal is acceptable, I could implement it.

[sighingnow]

After further research I found that there's no need to hack into furo itself.

Closing.