fix: add missing param in documentation

src/index.js

@@ -31,6 +31,7 @@ const PRIVATE_TOKEN = process.env.GITLAB_API_TOKEN;
  *
  * @param {*} externalLocation the URL for the raw openapi spec file.
  * @param {*} localPath the location where the downloaded spec should be saved
+ * @param {boolean} isPrivate optional, whether an external spec is in a private GitLab repository and should use secret token for access
  */
 async function pullExternalSpec(externalLocation, localPath, isPrivate = false) {
   let retries = 0;