feat(dev-tools): Mise en place phpcs+phpstan (#4777)

Co-authored-by: JamesRezo <james@rezo.net>
Reviewed-on: https://git.spip.net/spip/safehtml/pulls/4777


Co-authored-by: JamesRezo <jamesrezo@noreply.git.spip.net>
Co-committed-by: JamesRezo <jamesrezo@noreply.git.spip.net>