Expose original event in onDayChange in DayPickerInput

[wataru358]

First of all, this is great library and APIs makes so much sense to actual usage. This is 3rd one I tried, and it has been super fun to work with react-day-picker. A+++

onDayChange(day, modifier, dayPickerInput, originalEvent)

Is your feature request related to a problem? Please describe.
I'd like to change how to handle input value change based on what key user types.
By adding original event object as 4th arguments, I can access key prop at the same time access public method. So that I can, for example, on ESC, retrieve cached data from state and apply that, or on Enter key, just call hideDayPicker, etc.

Describe the solution you'd like
A clear and concise description of what you want to happen.

Describe alternatives you've considered
Combine inputProps onKeyDown event, but it seemed not straight forward.

Thanks again for a great package