This is a WIP that takes some of the nav styles we've previously used in our docs navbar and the Offcanvas navigation, and puts some enhancements into it for wider use. I'm sure there's something problematic about this, but feels like it could be a nice little addition to our navs.
Thoughts @twbs/css-review?
Preview: https://deploy-preview-31740--twbs-bootstrap.netlify.app/docs/5.0/components/navs/#nav-scroll