Updated readme to include a note about linux users (dunglas#37)

* Updated readme to include a note about linux users

* Fixed typo and moved section before Credits

* Updated section title

* Use title case in the title

Author: vonalbert

README.md

@@ -96,6 +96,10 @@ Zend Engine v3.2.0, Copyright (c) 1998-2018 Zend Technologies
     with Xdebug v2.6.0, Copyright (c) 2002-2018, by Derick Rethans
 ```
 
+### Editing Permissions on Linux
+
+If you work on linux and cannot edit some of the project files right after the first installation, you can run `docker-compose run --rm app chown -R $(id -u):$(id -g) .` to set yourself as owner of the project files that were created by the docker container.
+
 ## Credits
 
 Created by [Kévin Dunglas](https://dunglas.fr) and sponsored by [Les-Tilleuls.coop](https://les-tilleuls.coop).