Consider adding focus-visible package

[shanberg]

:focus-visible is a new-ish css pseudo-class that is designed to apply to focused elements for keyboard users, not apply for mouse users. It isn't well-supported yet, but the polyfill is popular and small, 10k unminified.

We have a couple complicated css selectors in the library right now that try to avoid the focus issue, but they're gross: :focus:not(:hover) and don't provide the full functionality of :focus-visible.

From the GitHub project:

Based on the proposed CSS :focus-visible pseudo-selector, this prototype adds a focus-visible class to the focused element, in situations in which the :focus-visible pseudo-selector should match.

The package: https://www.npmjs.com/package/focus-visible

I'm interested in your thoughts, @tilleryd, on adding a new package to the library.

[tilleryd]

I'm ok with this package. Hopefully Chrome will support it soon, it's not clear what the hold up is. Since Edge is moving to Chromium, eventually our top 3 browsers will support it natively.