Expose loadOptions of react-select

[carstenblt]

I wan't to write a select component that queries an API for options. You published a nice tutorial how to do that here: https://www.youtube.com/watch?v=Efn9OxSjA6Y&t=14s

react-select also has the ability to load options on the fly while typing: https://react-select.com/async

It would be really great if the SelectInput component would provide that interface as well.