message: Clarify typeguard usage
diff: @@ -180,6 +180,8 @@ export class ElasticSearchSearchEngine implements SearchEngine {
  * import { Client } from '@elastic/elasticsearch';
  *
  * const client = searchEngine.newClient<Client>(options => {
  + * // This typeguard ensures options are compatible with either OpenSearch
  + * // or Elasticsearch client constructors.
  * if (!isOpenSearchCompatible(options)) {
  * return new Client(options);
  * }
  