Implement docker packaging

[mdedetrich]

What is currently missing?

Docker packaging via https://github.com/sbt/sbt-native-packager

How could this be improved?

sbt-native-packager has already been implemented in #83 so it should be fairly straight forward. https://sbt-native-packager.readthedocs.io/en/stable/formats/docker.html has documentation for it.

Is this a feature you would work on yourself?

• I plan to open a pull request for this feature