docs: add versioning readmes

lib/versioning/cargo/readme.md

lib/versioning/composer/readme.md

lib/versioning/docker/readme.md

lib/versioning/hashicorp/readme.md

lib/versioning/loose/readme.md

lib/versioning/maven/readme.md

lib/versioning/node/readme.md

lib/versioning/npm/readme.md

lib/versioning/pep440/readme.md

lib/versioning/ruby/readme.md

lib/versioning/semver/readme.md

test/versioning/versioning-readmes.spec.js