update the contributing link in /demo/REAMD.md

demo/README.md

@@ -4,4 +4,4 @@ To check out how canaille looks like, or to start contributions, just run the de
 - with `docker-compose up` to install and run it in preconfigured docker containers
 - or with `./run.sh` to install it natively in a virtual environment and run it locally!
 
-Please check the details on [the documentation](https://canaille.readthedocs.io/en/latest/contributing.html).
+Please check the details on [the documentation](https://canaille.readthedocs.io/en/latest/development/contributing.html).