Add link to PyData Helsinki (#11)

Co-authored-by: Hugo van Kemenade <[email protected]>

Author: fohrloop

index.md

@@ -120,4 +120,6 @@ can approach one of the organisers directly or email
 - Our friends at [Archipylago](https://archipylago.dev/) down the road in Turku host
   monthly meetups and sprints for Python people.
 
+- The [PyData Helsinki](https://pydata-helsinki.github.io/) arranges data and machine-learning focused Python meetups in Helsinki.
+
 - Visit [Techtribes](https://www.techtrib.es/) to find more tech meetups in Finland.