Starter Workflow for Publishing Docker Images

Could you add a starter workflow (e.g., publish-docker.yml) that demonstrates the common task of building a Docker image from a repository's Dockerfile and publishing it to a container registry? This workflow should ideally show basic examples for pushing to popular registries like Docker Hub and GitHub Container Registry (ghcr.io), including placeholders for secure credential handling. Having this starter workflow would greatly simplify the setup process for developers looking to automate their container image deployment using GitHub Actions.

Start by reviewing the starter workflow patterns in this repository, then plan the new publish-docker.yml around building from the repository's Dockerfile. Done means the workflow demonstrates publishing to Docker Hub and ghcr.io with secure credential placeholders and is suitable as a reusable starter example.