Docker build automation

[elamperti]

We have to make sure the docker builds are triggered after code is merged into master. It'd be useful to use/set tags as mentioned in issue #6.

Thanks @fredkilbourn for noticing!

[elamperti]

We may use Github packages for this!

https://help.github.com/en/packages/using-github-packages-with-your-projects-ecosystem/configuring-docker-for-use-with-github-packages