[Feature]: first day of the week in datepicket within json form

[phantom943]

Is there an existing issue for this?

• I have searched the existing issues

Summary

Hello!
Akin to a Datepicker widget (see this issue), it would only be logical to allow to change first week day on a Datepicker widget within a JSON form.

Why should this be worked on?

Right now, the inability to customize the JSON form's datepicker forces us to resort to using a plain form, and to skip the features of the awesome JSON form)