nixos/doc: document documentation.man changes in 22.05 rel notes

nixos/doc/manual/from_md/release-notes/rl-2205.section.xml

@@ -163,6 +163,20 @@
           ~100MB for python itself).
         </para>
       </listitem>
+      <listitem>
+        <para>
+          <literal>documentation.man</literal> has been refactored to
+          support choosing a man implementation other than GNU’s
+          <literal>man-db</literal>. For this,
+          <literal>documentation.man.manualPages</literal> has been
+          renamed to
+          <literal>documentation.man.man-db.manualPages</literal>. If
+          you want to use the new alternative man implementation
+          <literal>mandoc</literal>, add
+          <literal>documentation.man = { enable = true; man-db.enable = false; mandoc.enable = true; }</literal>
+          to your configuration.
+        </para>
+      </listitem>
     </itemizedlist>
   </section>
   <section xml:id="sec-release-22.05-notable-changes">

nixos/doc/manual/release-notes/rl-2205.section.md

@@ -60,6 +60,8 @@ In addition to numerous new and upgraded packages, this release has the followin
   This has the added benefit to reduce the closure size of `ipython` from ~400MB to ~160MB
   (including ~100MB for python itself).
 
+- `documentation.man` has been refactored to support choosing a man implementation other than GNU's `man-db`. For this, `documentation.man.manualPages` has been renamed to `documentation.man.man-db.manualPages`. If you want to use the new alternative man implementation `mandoc`, add `documentation.man = { enable = true; man-db.enable = false; mandoc.enable = true; }` to your configuration.
+
 ## Other Notable Changes {#sec-release-22.05-notable-changes}
 
 - The option [services.redis.servers](#opt-services.redis.servers) was added