combobox needs focus set on list of choices for a11y support

[Becky Gibson]

Need to actually set focus to the items as move through them with the keyboard. The current implementation only changes the style. Thus, each item in the list will need an initial tabindex=-1

need to add the waiRole=combobox to the input field that gets focus

This will need additional work that I (Becky) can't explicitly specify at the moment. The list of items may need to be enclosed within a group role. I'll create another issue as necessary once this one gets closed.