Add basic pre-commit config

.github/workflows/docker-push.yml

.pre-commit-config.yaml

klaus/cli.py

klaus/ctagsutils.py

klaus/diff.py

klaus/highlighting.py

klaus/repo.py

klaus/templates/repo_list.html

pyproject.toml

setup.py

tests/repos/scripts/dont-render

tests/repos/scripts/invalid_repo

tests/repos/scripts/no-newline-at-end-of-file

tests/repos/scripts/test_repo

tests/utils.py