GitHub Action for publishing Docker images

[han16nah]

Problem

Currently, docker images have to be built locally and then pushed to DockerHub. This adds extra work to the release process and is prone to errors.

Solution

Create a GitHub Action to publish HELIOS++ docker images (with Python bindings for different Python versions) to DockerHub with every Release.

Additional context

• https://docs.github.com/en/actions/publishing-packages/publishing-docker-images