Docker image for jbake v2.7.0

Great to see another release of jbake! 

As we are using the jbake docker image in our build pipeline, I'm wondering whether an updated docker image is also being planned. The current latest is version [2.7.0-rc.3](https://hub.docker.com/layers/jbake/jbake/2.7.0-rc.3/images/sha256-5cf2bd677675072fc43c3f76d0070a751053ba1b325157ae65ebc338efff8ecc) and is 4 years old. 