fix(dropdown): restore space bar and enter key item selection

[emyarod]

Closes #3913

This PR fixes a regression introduced in #3586 and restores enter key and space bar item selection for the dropdown

Previously (pre-v10.5) individual items in the dropdown list fired click events on Enter keypress when selected, and the selected item information could be extracted from the event object. This behavior was changed so that focus is no longer placed on the individual dropdown items and is instead kept fixed on the dropdown menu. So in order to get the currently selected item information, we need to explicitly get the selected item info (getCurrentNavigation) and call .select()

on a side note, it seems that dropdowns now have 2 tab stops due to a tabindex on the dropdown menu even while hidden. this should probably be addressed in a separate PR

Changelog

New

• NPE check for focused item before removing focus class
• keyboard navigation tests for semantic markup introduced in Dropdown a11y updates #3586

Changed

• select item after space/enter keypress
• ignore nonrelevant events in toggle method
• focus on trigger after item selection with keyboard

Testing / Reviewing

Ensure that keyboard selection of dropdown items functions properly

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[tw15egan]

Should we add something to prevent the screen from scrolling when the spacebar is pressed when the menu is open?

[emyarod]

added in latest commit @tw15egan

[asudoh]

LGTM 👍 - Thanks alot @emyarod for taking a look at this issue!

[tw15egan]

LGTM ✅