Linters for uniform code style

[lelemmen]

Describe the feature you'd like
Much of the code comments that I've written are also concerning code style and formatting. It would be really interesting to explore some options such that the formatting of the code is done automatically.

On the top of my head, I know that clang-format can check C++ code.

I think it would also be nice to combine this with another GitHub Actions check (@guacke, any thoughts on this?). However, we should try to find a middle-ground here, because asking new developers to format their code manually can quickly lead to frustration.