docs(guide): add ng-newsletter to weekly updates link

Closes angular#4793

Author: auser

docs/content/guide/index.ngdoc

@@ -165,6 +165,8 @@ The recipe for getting help on your unique issue is to create an example that co
 
 * **Daily updates:** [Google+](https://plus.google.com/u/0/+AngularJS) or [Twitter](https://twitter.com/angularjs)
 
+* **Weekly newsletter:** [ng-newsletter](http://www.ng-newsletter.com/)
+
 * **Meetups: **[meetup.com](http://www.meetup.com/find/?keywords=angularJS&radius=Infinity&userFreeform=San+Francisco%2C+CA&mcId=z94108&mcName=San+Francisco%2C+CA&sort=member_count&eventFilter=mysugg)
 
 * **Official news and releases: **[AngularJS Blog](http://blog.angularjs.org/)