Pre-commit hook does not check linting for unity test files

[lukasostendorf]

The current pre-commit hook configuration only runs the linter for files in the src/ directory:

From .pre-commit-config.yaml:

      hooks:
          - id: clang-format
            args: [-i]
            files: 'src/.*\.[ch]'

We also have to check for the unit test files within the tests/ directory. Otherwise the local linting may succeed and the github linting action still fails. However, I do not know how to exclude the tests/unity folder within the tests/ folder as it is done for the github workflow.