Subsystem: doc

• the COLLABORATOR_GUIDE
• and https://nodejs.org/en/get-involved/development/#landing-pull-requests

…should mention @evanlucas ' https://github.com/evanlucas/core-validate-commit as a helpful tool in validating commit messages.

It could be helpful even for contributors also.