Add a clean way to "configure" corfu & fussy

[jojojames]

https://github.com/minad/corfu/issues/177

Right now, we can enable fussy with company on some predicate. This provides pretty responsive typing as we're not doing fuzzy matching on the first few letters. We should try to support the same functionality for corfu.

Either a smarter completion-style that wraps this one or some advices on corfu itself, etc.