Add 'Teaching this lesson?' section to README

README.md

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 # parallel-python-workbench
 
     This is the lesson repository for parallel-python-workbench
+
+## Teaching this lesson?
+Do you want to teach parallel programming? This material is open-source and freely available. 
+Are you planning on using our material in your teaching? 
+We would love to help you prepare to teach the lesson and receive feedback on how it could be further improved, based on your experience in the workshop.
+
+You can notify us that you plan to teach this lesson by creating an issue in this repository. Also, it would great if you can update [this overview of all workshops taught with this lesson material](workshops.md). This helps us show the impact of developing open-source lessons to our funders.