Doc (#97)

* update readme with Authentication Guide & Release Notes

* fix a misspelling : separately

* fix missing newline before package

* add Go Report Card + update doc

Author: chemidy

README.md

@@ -1,5 +1,6 @@
 [![Build Status](https://travis-ci.org/firebase/firebase-admin-go.svg?branch=master)](https://travis-ci.org/firebase/firebase-admin-go)
 [![GoDoc](https://godoc.org/firebase.google.com/go?status.svg)](https://godoc.org/firebase.google.com/go)
+[![Go Report Card](https://goreportcard.com/badge/github.com/firebase/firebase-admin-go)](https://goreportcard.com/report/github.com/firebase/firebase-admin-go)
 
 # Firebase Admin Go SDK
 
@@ -43,6 +44,9 @@ requests, code review feedback, and also pull requests.
 
 * [Setup Guide](https://firebase.google.com/docs/admin/setup/)
 * [Authentication Guide](https://firebase.google.com/docs/auth/admin/)
+* [Cloud Firestore](https://firebase.google.com/docs/firestore/)
+* [Cloud Messaging Guide](https://firebase.google.com/docs/cloud-messaging/admin/)
+* [Storage Guide](https://firebase.google.com/docs/storage/admin/start)
 * [API Reference](https://godoc.org/firebase.google.com/go)
 * [Release Notes](https://firebase.google.com/support/release-notes/admin/go)