I have created a new pull request from my personal Github account. It is required that a pull request be opened from a personal account in order to allow edits from maintainers. The original pull request was opened from the utulsa team account.

This replaces #12025

Description

1. Remove TAB/SHIFT_TAB from script to allow browser to manage tabbing
   While the tab key moves focus appropriately in the dom order within this component. The focus is not visually discernible when the subnav is opened. Since the method to move back up within the dom tree is present via arrow keys and the link at the top of the subnav, I agree with the solution that was proposed in Drilldown Sub-Menus won't let you Tab/Shift Tab out of Sub-Menu #11641
   Broad information about keyboard best practice can be found here: https://www.w3.org/TR/wai-aria-practices/#kbd_generalnav
2. Set root ul visibility:hidden and set subnav to visibility:visible when subnav is open

This will remove it from the dom allowing the user to tab into the next component/area when the subnav is open/visible

Add .visible class for use in drilldown subnav when opened.
These changes are recommented by https://github.com/ntdonley in #11641

...

• Closes Drilldown Sub-Menus won't let you Tab/Shift Tab out of Sub-Menu #11641

Types of changes

• Documentation
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (anything that would change an existing functionality)
• Maintenance (refactor, code cleaning, development tools...)

Checklist

• I have read and follow the CONTRIBUTING.md document.
• The pull request title and template are correctly filled.
• The pull request targets the right branch (develop or develop-v...).
• My commits are correctly titled and contain all relevant information.
• I have updated the documentation accordingly to my changes (if relevant).
• I have added tests to cover my changes (if relevant).