This is heavily WIP and will need some JS work to make it perfect. Mobile behavior will be crucial IMO and ultimately makes or breaks this entire effort. This PR adds some basic submenu positioning (not with Popper) and displaying via CSS.
Here's how we'd need to do it right:
- On mobile, submenus are toggled via click. Submenus could either expand inline, or overlapping the previous menu somehow. I swear I saw this on iOS but I cannot find an example now.
- Keyboard navigation would need to be added via JS. Left and right arrows would need to be able to open and close a submenu.
- If possible, having a safe zone for the cursor to move from main menu to submenu without any jankiness would be ideal.
Would love to hear from @twbs/js-review and the rest of the team on doing this.