Review alternatives to Slim Select

[tcompa]

We should review whether alternatives exist, and what are their pros and cons.
On top of available features, we should also consider how easy/hard testing is.

[tcompa]

(for the record, there is a new major release out https://github.com/brianvoe/slim-select/releases/tag/v3.0.0 - we should check whether it matters for this discussion)