Fix config path name, add dockerfile, add workflow.

.github/workflows/publish_docker_image.yml

@@ -33,7 +33,7 @@ jobs:
         uses: docker/metadata-action@9ec57ed1fcdbf14dcef7dfbe97b2010124a938b7
         with:
           images: |
-            grmrgecko/osc-mqtt-bridge
+            my-docker-hub-namespace/my-docker-hub-repository
             ghcr.io/${{ github.repository }}
       
       - name: Build and push Docker images