code: function _generateManifest(siteChecksums, presignedPosts) {
    return Utils.reduce(siteChecksums, (memo, checksum, path) => {
      /* eslint-disable-next-line no-param-reassign */
      memo[path] = presignedPosts[path].digest;
      return memo;
    }, {});
  }
docs: Generate a manifest
  @param {Object} siteChecksums
  @param {Object} presignedPosts
  @return {Object} manifest