doc: document Go 1.9.6

Change-Id: I9699b22d3a308cda685aa684b32dcde99333df46
Reviewed-on: https://go-review.googlesource.com/110315Reviewed-by: Filippo Valsorda <filippo@golang.org>

doc/devel/release.html

@@ -88,6 +88,13 @@ See the <a href="https://github.com/golang/go/issues?q=milestone%3AGo1.9.5">Go
 1.9.5 milestone</a> on our issue tracker for details.
 </p>
 
+<p>
+go1.9.6 (released 2018/05/01) includes fixes to the compiler and go command.
+See the <a href="https://github.com/golang/go/issues?q=milestone%3AGo1.9.6">Go
+1.9.6 milestone</a> on our issue tracker for details.
+</p>
+
+
 <h2 id="go1.8">go1.8 (released 2017/02/16)</h2>
 
 <p>