Enable containerization

[PolygeneLubricants]

We need to containerize JustPlanningPoker to enable simple deployment for third-party hosters, and support orchestration tools like Docker and Kubernetes. This will make life easier for developers to run the application locally in a consistent environment and will facilitate seamless deployment in different environments.

Acceptance Criteria:

• The application can be successfully built and run using Docker.
• Documentation is updated to cover build, run, and deployment instructions.
• (Optional) CI/CD pipeline is updated to handle container builds and pushes.
• Add current planningpoker CI/CD as actions in this repo.

[jonas-lomholdt]

I see you don't have infrastructure and deployment workflows as part of this repo. Would you consider moving that here so we can contribute?

[PolygeneLubricants]

That's a good idea, let me add that as an acceptance criteria. It's currently sitting in a private repo, for no good reason!