Adjust date based on Moon sighting

[moosalim]

Thanks for this plugin, Jazak Allah Khair

I believe there should be a way to correct the date if there is a need to so so, based on moon sighting. Please try to add this feature as it is very important.

I suggest adding method similar to the flutter standard one : DateTime.now().add(Duration(days: -1))

So, for for hijri it can be like this HijriCalendar.now().add(Duration(days: -1))

May Allah reward your work.