Make `onChange` function potentially asynchronous

[wowczarczyk]

Feature Request

Describe the problem related to this feature request

onChange should potentially be async and handled that way

Describe the solution you'd like

This library could await until onChange resolves and display its alerts when the processing is done

[panz3r]

Hi @wowczarczyk,

Thanks for feedback, whilst I understand the change you are requesting, I'd like to know more about your use-case, in particular what are you trying to achieve? and how having onChange async would help you?

[wowczarczyk]

I wanted to show the snackbar message after the file was actually uploaded, but found another way of dealing with this situation so I am all good with closing this issue