Add styles for details component

[Josh-Cena]

From the discussion: https://github.com/facebook/docusaurus/discussions/5749

Currently we reuse the Infima alert class name in Docusaurus, which is too noisy (blue background). There seems to be a few good designs proposed in that thread.

[Josh-Cena]

See https://github.com/facebook/docusaurus/issues/6632 also for a current CSS ordering defect we have. Not sure if that should actually be fixed, but if we can have default styles for details that doesn't reuse alert, that issue could be solved as well.