docs: add datepicker dateType property to input schema

[MFori]

Add new datepicker allowAbsolute and allowRelative options dateType property to input schema specification. This is based on this issue: https://github.com/apify/apify-core/issues/15662 and part of

• Input schema PR: https://github.com/apify/apify-shared-js/pull/477
• Input schema PR: https://github.com/apify/apify-shared-js/pull/485
• (app) AdvancedDatePicker PR: https://github.com/apify/apify-core/pull/17465

This one will be merged as the last one.

[drobnikj]

Just note to do not fofget, the params were changes from is to allow

[MFori]

Added also example as we have with some other editors:

[MFori]

[MFori]

We have changed allowAbsolute/allowRelative properties to single property dateType with options absolute, relative and absoluteOrRelative as proposed here: https://apify.slack.com/archives/C010Q0FBYG3/p1730210649660309?thread_ts=1728907212.870409&cid=C010Q0FBYG3

So I will ask you for one more review round 🙏 😁