callback to use upload state

[quentindemetz]

Hello and thanks for this library which works great out of the box.

I would like to render a progress bar with upload status, but I don't want to put the progress bar HTML inside the "render" function because I want to put it elsewhere (in the page header for example).
React doesn't allow to set state inside the "render" function.

Is there a set of props I can use for this ?

Thanks you