Calendar windower

[davidselassie]

It would be a nice convenience to have a window definition which buckets by the calendar. This isn't possible to do nicely with current tumbling windows because of: leap seconds, DST, differing month lengths, leap years, etc.

Parse into a datetime, read out the appropriate field. Maybe add some convenience ones.

CalendarWindower(unit: Literal["hour", "day", "week", "month", "half", "quarter", "year"], count: int = 1)