Add build and push Docker image step to changelog workflow

[hsiangjenli]

Enhance the changelog workflow by adding a new step to build a Docker image and push it to Docker Hub.

Proposed steps:

1. Update the changelog workflow YAML to include a step that builds a Docker image after changelog generation.
2. Add a subsequent step to push the built Docker image to Docker Hub.
3. Ensure all necessary Docker Hub credentials/secrets are referenced securely in the workflow.
4. Update documentation if needed to describe the new workflow steps.

Outcome:
The changelog workflow will automatically build and push a Docker image to Docker Hub, streamlining the release process.