release-notes: add postfixadmin module addition

nixos/doc/manual/from_md/release-notes/rl-2111.section.xml

@@ -199,6 +199,14 @@
           <link linkend="opt-services.xserver.displayManager.sx.enable">services.xserver.displayManager.sx</link>
         </para>
       </listitem>
+      <listitem>
+        <para>
+          <link xlink:href="https://postfixadmin.sourceforge.io/">postfixadmin</link>,
+          a web based virtual user administration interface for Postfix
+          mail servers. Available as
+          <link linkend="opt-services.postfixadmin.enable">postfixadmin</link>.
+        </para>
+      </listitem>
     </itemizedlist>
   </section>
   <section xml:id="sec-release-21.11-incompatibilities">

nixos/doc/manual/release-notes/rl-2111.section.md

@@ -60,6 +60,8 @@ subsonic-compatible api. Available as [navidrome](#opt-services.navidrome.enable
 
 - [sx](https://github.com/earnestly/sx), a simple alternative to both xinit and startx for starting a Xorg server. Available as [services.xserver.displayManager.sx](#opt-services.xserver.displayManager.sx.enable)
 
+- [postfixadmin](https://postfixadmin.sourceforge.io/), a web based virtual user administration interface for Postfix mail servers. Available as [postfixadmin](#opt-services.postfixadmin.enable).
+
 ## Backward Incompatibilities {#sec-release-21.11-incompatibilities}
 
 - The `paperless` module and package have been removed. All users should migrate to the