ci: tag new containers with the latest tag

Author: ethomson

.github/workflows/main.yml

@@ -70,7 +70,9 @@ jobs:
           BASE_ARG="--build-arg BASE=${{ matrix.container.base }}"
         fi
         docker build -t ${{ env.docker-registry-container-sha }} ${BASE_ARG} -f ${{ env.dockerfile }} .
+        docker tag ${{ env.docker-registry-container-sha }} ${{ env.docker-registry-container-latest }}
         docker push ${{ env.docker-registry-container-sha }}
+        docker push ${{ env.docker-registry-container-latest }}
       working-directory: ${{ env.docker-config-path }}
       if: github.event_name != 'pull_request' && env.docker-container-exists != 'true'