Add an event markdown to template facilitate creation of event

The markdown file could be copy/pasted and used as a basis to write
manually an event for the calendar.

Author: AbcSxyZ

event-template.md

@@ -0,0 +1,8 @@
+## Title of your event
+
+- Begin: dd/mm/yyyy hh:mm UTC+1
+- End: dd/mm/yyyy hh:mm UTC+1
+- Location: https://link-to-visio.org
+- Categories: category 1, category 2
+
+Description of your event.