README.md: add website link

README.md

@@ -2,15 +2,8 @@
 
 [![cc_by_sa](./img/cc_by_sa.png)](http://creativecommons.org/licenses/by-sa/4.0/)
 
-## Understanding a computer
+All the materials are accessible at the following url:
 
-## First steps with a terminal
-
-## What is a process
-
-## The network
-
-## Files manipulation
-
-## Processes manipulation
+[https://perso.ens-lyon.fr/laurent.modolo/unix/](https://perso.ens-lyon.fr/laurent.modolo/unix/)
 
+You can join us on the dedicated matrix channel (ask [laurent.modolo@ens-lyon.fr](mailto:laurent.modolo@ens-lyon.fr))
\ No newline at end of file