Add VEvent.GetDtStampTime as a partner to VEvent.SetDtStampTime. It is currently possible to read out the value using GetProperty, but the getTimeProp helper function -- that is used to parse different time formats for other get methods -- is not exported.
This is related to issue https://github.com/arran4/golang-ical/issues/79.
This adds VEvent.GetDtStampTime.