Suggestion: make recurring spec annotation compat with rrules

[azman0101]

What about supporting rfc5545 rrule in annotations ?

There is a use-case:

To implement a loosely coupled support of calendar (eg. Google Calendar) based scheduling of kube-downscale. This would be great if kube-downscaler directly support rrules.

What do you think about it @hjacobs ?

Regards

[hjacobs]

SGTM, a calendar integration would actually be nice 😄