public void addManifest(ManifestDescriptorTemplate manifest) {
    if (manifests == null) {
      manifests = new ArrayList<>();
    }
    manifests.add(manifest);
  }
Adds a manifest.

@param manifest a manifest descriptor
jib-core/src/main/java/com/google/cloud/tools/jib/image/json/V22ManifestListTemplate.java