Support for Monthly Schedules

As far as I can see, there is no way to do monthly schedule. CYCLIC does not help as timedelta does not support months. Since you do lots of type checking, not even my workaround works (pretty sure it would otherwise):

from dateutil.relativedelta import relativedelta #package python-dateutil
job = scheduler.cyclic(relativedelta(months=1),   # type: ignore 

To go further, I'd actually like to be able to implement custom timer logic. I would like to schedule a job monthly, but not on weekends or holidays