Role "listbox" causes some aria issues

[jtstothard]

I spotted this one when running an axe check on my code, it flagged up that you couldn't have a role="separator" as a child of a role="listbox". I also have another issue of this when using a role="progressbar" as a child of a "listbox". Is "listbox" the correct role for the top level list or does that suit the "list" component better?

dequelabs/axe-core#3938