listbox does not implement listbox a11y pattern

[Simon Oberhammer]

the listbox fits the listbox pattern

but does not properly implement it. we were able to subclass and monkey-patch some of the problems:

• listbox must have role=listbox
• children of listbox muste have role=option and a unique id
• keyboard controls for virtual focus managment (arrow keys) and aria-activedescendant as described in the pattern

what we could not easily change:

• buttons used as role=option should have aria-selected and not aria-pressed states