Add difficulty

Author: richelbilderbeek

docs/sessions/rsync/README.md

@@ -63,6 +63,23 @@ It works under Linux, Mac and Windows.
 
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+HPC Cluster|Difficulty|Reason
+-----------|----------|-----------------------------
+Alvis      |Medium    |No specialized documentation
+Berzelius  |Easy      |Has specialized documentation
+Bianca     |Easy      |Has specialized documentation
+COSMOS     |Medium    |No specialized documentation
+Dardel     |Medium    |No specialized documentation
+Kebnekaise |Easy      |Has specialized documentation
+LUMI       |Easy      |Has specialized documentation
+Rackham    |Easy      |Has specialized documentation
+Tetralith  |Easy      |Has specialized documentation
+Vera       |Easy      |Has specialized documentation
+
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 ### Exercise 1: transfer a file
 
 Use the documentation of your HPC cluster.