Add a CI job that runs uncrustify and checks for modifications

Sander, Oliverrequested to merge
introduce-uncrustify-ci-job into master

If modifications are found this means that the style rules are violated.

The uncrustify configuration file is the one from

https://dune-project.org/share/dune-uncrustify.cfg

downloaded on Jan 5. 2024.

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