Add CSC20 to list of training schools

Author: klieret

_data/training-schools.yml

@@ -212,3 +212,9 @@
   end_date: 2020-08-12
   source: https://indico.scc.kit.edu/event/721/registrations/266/
   title: MCnet-CTEQ summer school 2020
+- author: Kilian Lieret
+  date: 2020-08-23
+  deadline: 2020-04-05
+  end_date: 2020-09-05
+  source: https://indico.cern.ch/event/885686/
+  title: 43rd CERN School of Computing 2020