Update README.md

Add call to action to contact us.

Author: jdupak

README.md

@@ -5,6 +5,8 @@
 Developed by the [Computer Architectures Education](http://comparch.edu.cvut.cz) project
 at [Czech Technical University](http://www.cvut.cz/).
 
+**Are you using QtRvSim at your organization?** [Please, let us know in the discussion!](https://github.com/cvut/qtrvsim/discussions/136)
+
 ## Table of contents
 
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