This would implement https://core.trac.wordpress.org/ticket/28721

A snapshot should be scheduleable from the the Customizer via something like a “Schedule” button along with a timestamp for when it should apply.

If there is also an edit post screen for viewing a snapshot in the admin ( #18), the snapshot should also be able to be scheduled using the traditional post scheduling functionality.