insert_event (#1)

Option to insert events seems to work.

Reviewed-on: bjoernf/ics_analyzer#1
Co-authored-by: bjoernf <bjoern.foersterling@web.de>
Co-committed-by: bjoernf <bjoern.foersterling@web.de>

docs/ics_format.txt

@@ -0,0 +1,33 @@
+ICS files from Microsoft Outlook differ from those that were created by Gnome Evolution.
+(semicolons are used instead of colons at some position)
+
+Evolution
+---------
+all line endings are \r\n
+
+all day event:
+DTSTART;VALUE=DATE:20230908
+DTEND;VALUE=DATE:20230909
+
+an all day event can span over multiple days and look like this:
+DTSTART;VALUE=DATE:20230911^M$
+DTEND;VALUE=DATE:20230916^M$
+
+appointment:
+DTSTART;TZID=/freeassociation.sourceforge.net/Continent/City:
+ 20230909T090000
+DTEND;TZID=/freeassociation.sourceforge.net/Continent/City:
+ 20230909T093000
+
+appointments can also span over multiple days:
+DTSTART;TZID=/freeassociation.sourceforge.net/Europe/Berlin:
+ 20230913T230000
+DTEND;TZID=/freeassociation.sourceforge.net/Europe/Berlin:
+ 20230914T040000
+
+SEQUENCE is the number of times the event was modified.
+Evolution sets this to 2 after it has been generated.
+
+Appointments include the continent and city of the used time zone.
+
+"DESCRIPTION:" is an optional field.