Expose date-based navigation method (supersedes goToToday request)

[MohammadAzimi]

Adds a method (available by ref) for programmatically navigating to any date. Passing new Date() enables go-to-today behavior while supporting additional use cases.

This implementation addresses all limitations raised in #386 and provides a more flexible alternative to a dedicated goToToday method.

• Surely the visible month should be updated by calling goToDate
• The isSelected boolean determines whether to just navigate or update the selected date
• The feature is disabled when the scrollable prop is set to true, to prevent any breaks. (I would try to implement it in another PR)

Closes #380

[peacechen]

Thanks @MohammadAzimi for this oft requested and useful feature!