Update README.md

Author: TomStanczyk

README.md

@@ -1,2 +1,6 @@
 # node-red-contrib-google
-Node-RED node for Google APIs. A wrapper for [google-api-nodejs-client](https://github.com/google/google-api-nodejs-client).
+Node-RED node for Google APIs. 
+
+A wrapper for [google-api-nodejs-client](https://github.com/google/google-api-nodejs-client).
+
+List of available APIs are provided online via [Google API Discovery Service](https://developers.google.com/discovery/).