[Proton Calendar] Support more ICAL rules like BYSETPOS
There are some events that happens "The third sunday of june" for example. This kind of rule doesn't really need an interface to edit/add as it's not something that often to add/change but even by using the import of VEVENT (ICAL), the RRULE is not correctly parsed and the event gets ignored. Is it possible to support those rules?
The current import capability does not support some recurrence rules, for examples "RRULE:FREQ=YEARLY;WKST=SU" fails to import. The error log does not include the name of the event, just the UID, making it difficult to determine which event failed to import.