summarize HMAC changes in "Improved Modules" as well

Author: picnixz

Doc/whatsnew/3.14.rst

@@ -623,6 +623,14 @@ http
   (Contributed by Yorik Hansen in :gh:`123430`.)
 
 
+hmac
+----
+
+* Add a built-in implementation for HMAC (:rfc:`2104`) using formally verified
+  code from the `HACL* <https://github.com/hacl-star/hacl-star/>`__ project.
+  (Contributed by Bénédikt Tran in :gh:`99108`.)
+
+
 imaplib
 -------