fix-end-date-printing (#2)

printing of the end date was fixed

Reviewed-on: bjoernf/ics_analyzer#2
Co-authored-by: bjoernf <bjoern.foersterling@web.de>
Co-committed-by: bjoernf <bjoern.foersterling@web.de>

docs/ics_format.txt

@@ -13,6 +13,8 @@ an all day event can span over multiple days and look like this:
 DTSTART;VALUE=DATE:20230911^M$
 DTEND;VALUE=DATE:20230916^M$
 
+The DTEND of an all day event is exclusively, it is not an all day event anymore!
+
 appointment:
 DTSTART;TZID=/freeassociation.sourceforge.net/Continent/City:
  20230909T090000