Invalid parse support of the `EXDATE` attribute

[oc-clem]

Hi there 👋,

First of all, thank you for this library, it helps a lot!

I encountered an issue while working with excluded dates.
I noticed a format difference between the RFC and the actual implementation while parsing the recurrence string.

According to the RFC 5545, the EXDATE should be written on a new line like this:

DTSTART:20210622T120000Z
RRULE:FREQ=WEEKLY;BYDAY=TU;UNTIL=20210712T120000Z
EXDATE:20210629T120000Z,20210706T120000Z

But, when I load this string in a new Rule(), it does not handle the excluded dates.
The Rule constructor expects an EXDATE like this:

DTSTART:20210622T120000Z
RRULE:FREQ=WEEKLY;BYDAY=TU;UNTIL=20210712T120000Z;EXDATE=20210629T120000Z,20210706T120000Z

For now, I used str_replace() to convert these excluded dates, but it could be great if the library auto handles both formats.

Thanks a lot and have a nice day!