Support shadow repository from build.yaml

Implementation from official Home Assistant builder:

    # Use shaddow repository
    if bashio::var.has_value "${shadow_repository}"; then
        bashio::log.info "Generate repository shadow images"
        docker tag "${repository}/${image}:${version}" "${shadow_repository}/${image}:${version}"
        for tag_image in "${docker_tags[@]}"; do
            bashio::log.info "Create shadow-image tag: ${shadow_repository}/${image}:${tag_image}"
            docker tag "${repository}/${image}:${version}" "${shadow_repository}/${image}:${tag_image}"
            push_images+=("${shadow_repository}/${image}:${tag_image}")
        done
        push_images+=("${shadow_repository}/${image}:${version}")
    fi

From builder.sh.