Matches the formatting that release-please produces. Using the same
formatting for previous entries prevents release-please from overwriting
(deleting) previous entries when it updates the CHANGELOG.

Automatically creates/updates release PRs when there are new commits
on a given branch of the repository (currently configured as `master`).

Semver hints in commit messages can let release-please know
whether to draft a minor or major release, but otherwise the
release proposal PR will be for a semver patch-level release by default.

Co-authored-by: gengjiawen <technicalcute@gmail.com>

Link to the "How should I write my commits?" section of release-please's
README.md, rather than the NodeJS commit guidelines.

We don't actually have a Travis CI config file (`.travis.yml`) anymore,
and this would be redundant to the "ci" prefix anyway.

More subcommands of node-gyp, and more OSes.

Also add documentation comments in the .yml file
explaining the categories and order of the prefix entries.