[TASK] Add php-cs-fixer as require-dev dependency

To increase usage of php-cs-fixer and to integrate it easily
to our build chain, the PSR-2 CGL tool php-cs-fixer that was
used for the main transition is added as require-dev dependency.
This way we can have an eye on the dependency and don't
require a global installation.

Change-Id: Icb2703e564de06e8ffd308117bb92aa8c4a5d12a
Resolves: #76961
Releases: master
Reviewed-on: https://review.typo3.org/48828


Tested-by: Bamboo TYPO3com <info@typo3.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Tested-by: Andreas Fernandez <typo3@scripting-base.de>