Add linting for C++ code

[echeran]

We should add a C++ linter, as #228 suggests. According to #228 (comment), the industry standard is clang-tidy.

We should ensure that the dependencies for this are in our setup script, and that we add this to CI (or our end-to-end script in CI).

[sven-oly]

What about this GItHub action? https://github.com/HorstBaerbel/action-clang-tidy

[sven-oly]

Applying this command fixes some things:
clang-tidy --checks='modernize*, readability*' *.cpp --fix-errors

[sven-oly]

Does this mean we would apply C++ linting in the continuous integration?

[sffc]

Yes, we should enforce the C++ linting in GitHub Actions.