Please add a TextStyle for dates outside the selected month

[ma-ruz]

When showNextMonthStart and/or showPrevMonthEnd are turned on, it would be fine to be able to display the added days in a different TextStyle. Please add it to DatePickerStyles.

[ma-ruz]

I solved it by using an eventDecorationBuilder which compares the date with the selected month which I have to store in onMonthChanged which needs the widget to be rebuilt (to apply the colors after switching the month) but I hope this is just a temporary solution as it can be much more easily implemented in the library.