if clearOnBlur:true, relatedTarget returns null when clicking on suggestions list

Nobody has claimed this yet.

What I'm trying to do:
- if `clearOnBlur:true`, and the `relatedTarget` on the blur event is the suggestions list, do not clear.

What happens instead:
- in the blur event, relatedTarget is `null` if user clicks on suggestions list.

Why?
- There is an event listener in `suggestions` that removes the suggestions list on selection, before the blur event occurs.

Suggested fix:
- Allow mapbox-gl-geocoder to override the event handling in `suggestions`, or add an option to `suggestions` that does not clear the list on selection.

Start by reproducing the blur behavior with clearOnBlur:true while clicking the suggestions list, then inspect the suggestions event listener and the blur event handling described in the issue. Done means selecting a suggestion no longer removes the list before the blur event can use its relatedTarget, while preserving the intended clearOnBlur behavior.

Written by the indexing model from the issue text.