Add Dockerfile

A Dockerfile would be useful. It would make it easy to build a docker image and create a container. This would make it simpler to deploy the project as it would eliminate the need to setup the VM, install Nodejs, and install other dependencies.

The README could contain basic docker commands to build the image and run it.

Open to reviewing a PR for this if it will help others. There are already several docker images for it, some linked in the wiki.