The checkstyle formatter is not part of the NPM package.

[hrmoller]

Please re-publish to NPM to make to the checkstyle formatter available in the NPM package.

[ehmicky]

The version is on npm is 2.0.0.alpha, which is the same as current one on GitHub.

However this is misleading, because the version published on npm is from this commit, which is 18 months and about 50 commits old.