Docker wrapper referenced in README is based on a fork

First, thank you all for your work on this excellent project.

The README references a [docker wrapper](https://github.com/microbox/node-url-to-pdf-api) that builds off a forked version of this repository at https://github.com/onesdk/url-to-pdf-api.

This is a bit misleading as it is 52 commits behind master, which means new fixes and features such as image rendering are not available. In the worst case, promoting a Docker image based on a fork could be a security risk.

Are you open to a PR to add a `Dockerfile` to this repository, or link to another Docker image that is based directly on this repository?