[release-branch.go1.12-security] doc: document Go 1.12.11

Change-Id: I73f27924046a0a2493330ddc732d1a2fd3f730a5
Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/575981Reviewed-by: Filippo Valsorda <valsorda@google.com>
Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/575985

doc/devel/release.html

@@ -105,6 +105,13 @@ See the <a href="https://github.com/golang/go/issues?q=milestone%3AGo1.12.10">Go
 1.12.10 milestone</a> on our issue tracker for details.
 </p>
 
+<p>
+go1.12.11 (released 2019/10/17) includes security fixes to the
+<code>crypto/dsa</code> package.
+See the <a href="https://github.com/golang/go/issues?q=milestone%3AGo1.12.11">Go
+1.12.11 milestone</a> on our issue tracker for details.
+</p>
+
 <h2 id="go1.11">go1.11 (released 2018/08/24)</h2>
 
 <p>