I am resigning from my role as maintainer of the `rippled` codebase.
Please update repository permissions accordingly, prior to merging this pull request.
Thanks to everyone who has contributed, especially those whom I had the opportunity to closely collaborate with.
* Add a new YAML file (.pre-commit-config.yaml) to set up pre-commit
hook for clang-format
* The pre-commit hook is opt-in and needs to be installed in order to
run automatically
* Update CONTRIBUTING.md with instructions on how to set up and use the
clang-format linter
Automating the process of running clang-format before committing code
helps to save time by removing the need to fix formatting issues later.
This is a tooling improvement and doesn't change C++ code.
