Evaluate accessibile autocomplete libraries

With the removal of Select2 (due to inaccessibility), we must write our own implementation or (better) evaluate a possible replacement. In particular, examine the GOV.uk accessible autocomplete widget.

See:
https://a11y-guidelines.orange.com/en/articles/autocomplete-component/
https://github.com/alphagov/accessible-autocomplete/
https://alphagov.github.io/accessible-autocomplete/examples/