docs(node): support "stable"/"preview" release level (#1312) (#56)

Author: gcf-owl-bot[bot]

packages/google-cloud-privatecatalog/README.md

@@ -125,6 +125,8 @@ This library follows [Semantic Versioning](http://semver.org/).
 
 
 
+
+
 More Information: [Google Cloud Platform Launch Stages][launch_stages]
 
 [launch_stages]: https://cloud.google.com/terms/launch-stages