Add Dockerfile and related Github Action

[Kimmax]

My use case requires running additional software in containers. I'm sharing my Dockerfile and GitHub Action in case they might be useful to make public.

They build both arm64 and amd64 minimal images (about 2 MB) on native runners and push them to the repo's GitHub Container Registry, which should be created automatically on the first run if it doesn't already exist. The build step uses a debian:bookworm-slim base image, following the compile steps from the native and cross action.

I also added a usage example to README.md and moved the Service Discovery section down to improve reading flow.

Thanks for maintaining this project 🚀