Create Docker Images for Tobira automatically

[KatrinIhler]

See #240

[mtneug]

There is already a Dockerfile. There are, however, no GitHub CI workflows to build container images automatically.

[mtneug]

And to be clear: I would add the GitHub CI workflow in the Tobira repository and not here.

[KatrinIhler]

Fair point, thanks for clarifying @mtneug :) But can we keep the issue here for now? Otherwise it doesn't show up on the HDN board ^^'