Add tag for versions #40

It would be great if releases would not just bump the version in package.json, but also have an associated tag in git for them. This would make reviewing changes a lot nicer, and improve also the information provided by automated systems such as dependabot.

It seems that there are some tags already, but not for all versions. Maybe the release procedure could include making the tag, possibly by using npm version (patch|minor|major) instead of manually touching package.json?