Some tweaks to ideally improve navigating across our documentation on narrow devices. This PR removes the navbar scroll that I had implemented and replaces it with our classic collapsing navbar, but with a slight twist. I've added column classes to stack the nav across two columns on mobile devices so that the opened nav isn't too tall.
Still need to adjust the menu toggles (missing some styles, tap targets could be larger, etc), but hoping to get some initial feedback from the team on overall direction. Also wondering if I should do more to condense the subnav (search, version picker, and sidebar toggle) on mobile views.
Any thoughts, feedback, or examples of other patterns would be appreciated!
/cc @twbs/css-review
Preview: https://deploy-preview-31119--twbs-bootstrap.netlify.app/