Some Improvements

[mrcwbr]

I'm using your picker and It's really great. But I have some improvements that'd be nice:

1. Render without a child: I control the open state programmatically (not via user interaction) so it would be nice to include the picker without the default button. I currently use the following workaround to stop rendering the default "show"-button:
   <DateRangePicker onChange={this.setDates} endDate={endDate} startDate={startDate} displayedDate={displayedDate} open={isDatePickerOpen} range> <></> </DateRangePicker>

2. Support of TypeScript would be nice (add a typescript declaration file and link it in you package.json - I think this should work: https://stackoverflow.com/a/51573845/6003494)

3. OnBackdropClick-Handler (clicking the backdrop (Black Background when the calendar is open) should fire an event, so I can handle it in my app)

If I have time the next days and you like the ideas I can contribute a PR for this issue.

Best regards
Marco