quote4#47 documentation for `~q()`

Stream: PR reviews

[Eric Wieser]

quote4#47 adds some basic documentation for some Qq features. While there's no bors on that repo and I have merge rights myself, it would be great to have another set of eyes skim over it for any mistakes / glaring gaps

[Eric Wieser]

(I'm not trying to write all the documentation here in one go, but at least provide some breadcrumbs for someone else to write something more coherent from in future)