Old topic sorry, but I thought that folks (and future googlers) might be interested that I've given mkdocs-quiz (the plugin mentioned above) a makeover and joined as a maintainer. It now lives here: https://github.com/ewels/mkdocs-quiz

The plugin has had a pretty complete rewrite and does the same thing, but hopefully a bit nicer now and with a bunch of new features (like a progress bar, and a confetti cannon when you finish the quiz).

The syntax is very similar to that requested by the OP:

<quiz>
Are you ready?
- [x] Yes!
- [ ] No!
- [ ] Maybe!

## Provide some additional content
This is shown after answering.
</quiz>

It's designed to work best with mkdocs-material