coding-style: update to describe qmlformatting

jami-client-qt#1059
Change-Id: I8878139027267a798c092055a84ceac87dd21040

developer/coding-style.md

@@ -7,5 +7,8 @@ developers that want to integrate some code to Jami **
 C++ format rules are defined by this clang-format file:
 https://git.jami.net/savoirfairelinux/jami-daemon/blob/master/.clang-format
 
+QML format rules are defined by the source code used to build the qmlformat executable:
+https://codebrowser.dev/qt6/qtdeclarative/tools/qmlformat/qmlformat.cpp.html
+
 All developers are recommended to format their code using the script in `jami-project/scripts/format.sh`.
-This is done automatically (as a pre-commit hook) when using `./build.py --init`
+This is done automatically (as a pre-commit hook) when using `./build.py --init --qt=<path-to-qt>`.