add github workflow to build and push to docker hub

[iosefa]

Add GitHub actions to publish to Docker Hub

Problem
There is no automated deployment process for pushing images to Docker Hub. This requires manual steps to build, tag, and publish Docker images, leading to potential inconsistencies and delays.

Improvement
Automate the process of building and publishing Docker images to Docker Hub using GitHub Actions. The workflow should:

1. Trigger on commits to specific branches (e.g., main or release).
2. Build the Docker image.
3. Tag the image appropriately (e.g., using the Git commit SHA or semantic versioning).
4. Push the image to Docker Hub.

Look at the proposed GH Action for pgRouting and the existing for PostGIS for inspiration.

Alternatives

1. Manual Deployment

• Pros: No additional setup required.
• Cons: Error-prone, time-consuming, and inconsistent.

2. Third-Party CI/CD Tools

• Pros: Tools like Jenkins, CircleCI, or GitLab CI/CD can achieve the same result.
• Cons: Adds complexity and external dependencies when GitHub Actions is already integrated into the project.