Adding a configuration to invoke clang-format v13 on all modified files
as part of the commit process, and a new script file `setup-env.sh` to
manage installing the pre-commit hook.
The hook is installed using a local python venv to ensure the correct
version of clang-format is used. This approach also enables the hook to
be installed on any platform which supports python although the setup
script is limited to platforms which support bash.
