Don't replace timezone of all day events

- This fails as defined by ics-py (you would think that event.floating
  would handle this, but apparently not).
- Also add a test for this

Author: rkdarst

tests/test_calendar.py

@@ -45,6 +45,9 @@ def test_calendar_default_timezone():
               - summary: February 1
                 begin: 2022-02-01 00:00:00 +02:00
                 duration: {hours: 1}
+
+              - summary: Earth day (all day)
+                begin: 2022-04-22
             '''
         ))]
     )

yaml2ics.py

@@ -75,7 +75,7 @@ def event_from_yaml(event_yaml: dict, tz: tzinfo=None) -> ics.Event:
             ))
 
     event.dtstamp = datetime.utcnow().replace(tzinfo=dateutil.tz.UTC)
-    if tz and event.floating:
+    if tz and event.floating and not event.all_day:
         event.replace_timezone(tz)
     return event