doc/go1.16: add crypto/x509 CSR release note

Change-Id: If74d49c3be9299d8c136003673e0fee2a563389d
Reviewed-on: https://go-review.googlesource.com/c/go/+/268957
Trust: Roland Shoemaker <roland@golang.org>
Run-TryBot: Roland Shoemaker <roland@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Katie Hockman <katie@golang.org>
diff --git a/doc/go1.16.html b/doc/go1.16.html
index 2187f0b..a2f3989 100644
--- a/doc/go1.16.html
+++ b/doc/go1.16.html
@@ -354,6 +354,13 @@
   of a malformed certificate.
 </p>
 
+<p><!-- CL 233163 -->
+  A number of additional fields have been added to the
+  <a href="/pkg/crypto/x509/#CertificateRequest">CertificateRequest</a> type.
+  These fields are now parsed in <a href="/pkg/crypto/x509/#ParseCertificateRequest">ParseCertificateRequest</a>
+  and marshalled in <a href="/pkg/crypto/x509/#CreateCertificateRequest">CreateCertificateRequest</a>.
+</p>
+
 <h3 id="encoding/json"><a href="/pkg/encoding/json">encoding/json</a></h3>
 
 <p><!-- CL 263619 -->