Pandas version checks

• I have checked that the issue still exists on the latest versions of the docs on main here

Location of the documentation

https://pandas.pydata.org/pandas-docs/stable/user_guide/timeseries.html?highlight=abstractholidaycalendar#holidays-holiday-calendars

Documentation problem

We have a description of how the holiday stuff works in the user guide, but no associated reference manual documentation. I think the classes and functions mentioned there should be in the reference manual.

Suggested fix for documentation

Add reference manual entries for classes and functions in pandas/tseries/holiday.py