Add tabIndex to DayPicker types (#909)
Add tabIndex to DayPicker types (#909)

It looks like this is [included in the propTypes](https://github.com/gpbl/react-day-picker/blob/421af9f56b1b07ed58f864678b3bbb8617cdaff7/src/DayPicker.js#L92) for the component, but didn't get added to the typescript typings.
gpbl/react-day-picker,gpbl/react-day-picker,gpbl/react-day-picker