Sets or gets the latest date that an app user can select.
Setting maxDate prevents app users from selecting
dates past the maximum date.
Set maxDate to undefined to remove the
current maximum date limitation.
Getting maxDate returns the current maximum
date that an app user can select.
If a date is past the maximum date but is also set as an enabled date
with enabledDateRanges, the date is
disabled and the app user can't select the date in the date picker.
maxDate must be set before it can be retrieved.