doc: add App Engine docs to 'learn' and 'reference' pages

R=golang-dev, dsymonds
CC=golang-dev
https://golang.org/cl/5672048

doc/docs.html

@@ -51,6 +51,12 @@ the language specification, both of which should be read first.
 How to write a new package and how to test code.
 </p>
 
+<h3 id="appengine"><a href="http://code.google.com/appengine/docs/go/gettingstarted/">Getting Started with Go on App Engine</a></h3>
+<p>
+How to develop and deploy a simple Go project with
+<a href="http://code.google.com/appengine/">Google App Engine</a>.
+</p>
+
 <h3 id="go_faq"><a href="go_faq.html">Frequently Asked Questions (FAQ)</a></h3>
 <p>
 Answers to common questions about Go.

doc/reference.html

@@ -22,6 +22,12 @@ The built-in documentation for the Go tools.
 The official Go Language specification. 
 </p>
 
+<h3 id="appengine"><a href="http://code.google.com/appengine/docs/go/">App Engine Go Runtime Documentation</a></h3>
+<p>
+The documentation for
+<a href="http://code.google.com/appengine/">Google App Engine</a>'s Go runtime.
+</p>
+
 <h3 id="release"><a href="devel/release.html">Release History</a></h3>
 <p>A summary of the changes between Go releases.</p>