doc/contribute.html: link to wiki for more code review information

(from the discussions on CL 89650044)

LGTM=minux.ma, iant
R=iant, minux.ma
CC=golang-codereviews
https://golang.org/cl/97770043

doc/contribute.html

@@ -606,6 +606,13 @@ $ hg submit 99999
 local repository out of date; must sync before submit
 </pre>
 
+<h3>More information</h3>
+
+<p>
+In addition to the information here, the Go community maintains a <a href="https://code.google.com/p/go-wiki/wiki/CodeReview">CodeReview</a> wiki page.
+Feel free to contribute to this page as you learn the review process.
+</p>
+
 <h2 id="copyright">Copyright</h2>
 
 <p>Files in the Go repository don't list author names,