doc: document Go 1.13.5

Change-Id: I289d13ff0a01466d93ebc555eaa81273d4297eb4
Reviewed-on: https://go-review.googlesource.com/c/go/+/209841
Run-TryBot: Carlos Amedee <carlos@golang.org>
Reviewed-by: Alberto Donizetti <alb.donizetti@gmail.com>
Reviewed-by: Alexander Rakoczy <alex@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

doc/devel/release.html

@@ -63,6 +63,13 @@ See the <a href="https://github.com/golang/go/issues?q=milestone%3AGo1.13.4">Go
 1.13.4 milestone</a> on our issue tracker for details.
 </p>
 
+<p>
+go1.13.5 (released 2019/12/04) includes fixes to the go command, the runtime,
+the linker, and the <code>net/http</code> package. See the
+<a href="https://github.com/golang/go/issues?q=milestone%3AGo1.13.5">Go
+1.13.5 milestone</a> on our issue tracker for details.
+</p>
+
 <h2 id="go1.12">go1.12 (released 2019/02/25)</h2>
 
 <p>