Option to block out past dates in the date picker block

### Impacted plugin

Jetpack

### What

Option to block out past dates in the date picker

### How

Hello! We're using Jetpack for the forms on our site. The one form, in particular, is used for booking requests, and it would be amazing UI if we could have it grey out past dates when selecting a date in the `date picker` block.

While I recognise this isn't what everyone would want on a form, could we look into a block setting where we say something like "past dates are not selectable"?

Frontend:

Backend:

Thank you so much!

No files or tests are named. Start by locating the Jetpack date picker block and its existing block settings, then trace how the selected date is handled in the editor and frontend. Done means an optional setting prevents past dates from being selected while preserving the current behavior when disabled.

Written by the indexing model from the issue text.