bug: semantic PR check in CI not documented in CONTRIBUTING

[lucasgonze]

Description

On submitting a PR that matches the requirements in CONTRIBUTING.md, the submitter will get a failure based on the formatting of their commit message, but the formatting is not documented.

Current behavior

CI error on PR:

=== developer-toolkit-template-go === [ lint-commit      ]: Checking that commit messages are properly formatted...
f3551e1: subject does not match regex [(chore|docs|feat|fix|refactor|tests?)\s?(\([^\)]+\))?!?: .*]
make: *** [build/lint.mk:53: lint-commit] Error 1

Expected behavior

The contributor guidelines should communicate that subject must begin with a keyword followed by a colon.

Steps To Reproduce

Steps to reproduce the behavior:

1. Create a commit with message "Debug"
2. Submit PR
3. See error relating to commit formatting

Debug Output (if applicable)

Additional Context

https://github.com/newrelic/developer-toolkit-template-go/actions/runs/5546108613/jobs/10125939014?pr=11