Add a developer faq to the chill documentation

docs/source/development/FAQ.rst

@@ -0,0 +1,36 @@
+.. Copyright (C)  2014 Champs Libres Cooperative SCRLFS
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.3
+or any later version published by the Free Software Foundation;
+with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
+A copy of the license is included in the section entitled "GNU
+Free Documentation License".
+
+.. _faq:
+
+
+Frequently asked questions
+####################
+
+Continuous integration
+***********
+
+Pipeline fails, but php-cs-fixer doesn't alert me when running it locally ?
+========================================
+
+It is possible that you run php-cs-fixer on your local instance of chill and no fixes are made.
+Everything seems fine, so you push. However once the pipeline is run in gitlab, you're notified that it failed due to php
+cs errors.
+
+In this case it's likely that you have to update your version of php-cs-fixer.
+php-cs-fixer is installed when building the docker image: https://gitea.champs-libres.be/Chill-project/chill-skeleton-basic/src/branch/main/Dockerfile#L50
+
+Consequently, to update php-cs-fixer we have to update the image by building it again.
+
+For this the following commands can be used,
+
+.. code-block:: php
+
+docker compose build --pull php
+# replace existing containers
+docker compose up -d --force-recreate php