mention running of CWL from Cylc

[mr-c]

See also cylc/cylc-doc#240

[kinow]

Thanks @mr-c ! I think someone at $work mentioned CWL to @hjoliver a few days (weeks?) ago when talking about Cylc. Good timing!

From memory, this project used CWL + Cylc I think? But we indeed to not have anything mentioning CWL, nor giving any tips for users of Cylc on how to use CWL, so +1 :-)