readme: added calendar emoji to header

README.md

@@ -1,4 +1,4 @@
-# ical2vdir
+# ical2vdir 📅
 
 [![Code style: black](https://img.shields.io/badge/code%20style-black-000000.svg)](https://github.com/psf/black)
 [![Last Release](https://img.shields.io/pypi/v/ical2vdir.svg)](https://pypi.org/project/ical2vdir/#history)