Draft: ci: Add clang-format check
The second commit is there for demonstration purposes and will be removed when clang-format is added to the container, if we're ok with that.
I guess this could be added later to xfce4-dev-tools by testing if there's a .clang-format
file in the repository root, but for now it can be added to any project that decides to use clang-format.
Edited by Gaël Bonithon