New Accessible Dropdown Nav Bar Component

[danparnella]

Provides a contained and simple to stand up accessible navigation bar with a menu of parent links and optional child links hidden within submenus.

Known Issues

• If while in mobile view, a user opens some submenus, then closes the mobile menu and expands their browser to show the desktop view, the submenus will still be open and will need to be closed with the arrow buttons. We could allow for something to be passed down from the mobile menu button to trigger closing all submenus when the mobile menu is closed, but this seemed like a far enough out edge case (and a non-breaking issue) to avoid adding more complication to the component.

Author Checklist

• [x] Add unit test(s)
• [x] Update version in package.json (see the versioning guidelines)
• [x] Update documentation (if necessary)
• [x] Add story to storybook (if necessary)
• [x] Assign dev reviewer