Helpers related to universal accessibility
Universal accessibility is a core goal of the Elix project. These helpers are
used by mixins like AriaListMixin and
AriaMenuMixin to support accessibility via ARIA.
A dictionary mapping built-in HTML elements to their default ARIA role.
defaultAriaRole.ol returns "list", since the default ARIA role
ol (ordered list) element is "list".
If the given element already has an ID, return it. If not, generate a
previously unused ID and return that.