README: add feedback address

README.md

@@ -76,6 +76,10 @@ at <https://www.fi.muni.cz/tech/unix/print.html>.
 | Ubuntu 20.04 | Working |
 | ArchLinux    | Working |
 
+## Feedback
+
+If you have any question, please contact us at [unix@fi.muni.cz](mailto:unix@fi.muni.cz).
+
 ## Repository structure
 
 | File                     | Description                                      |