[FEATURE] Maximum selectable span

[enricobenedos]

In my case I need to give to user the possibility to select max 7 days span. At the moment the span selection is free. It will be a very good feature to add to this package, something like:

DateRagePicker.showDatePicker(
          context: context,
          …
          maxSelectableSpan: 7
)

[enricobenedos]

Closed due to deprecation.