nixos/release-notes: Improve 21.11 stub

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

@@ -12,8 +12,18 @@
       </para>
     </listitem>
   </itemizedlist>
+  <section xml:id="highlights">
+    <title>Highlights</title>
+    <para>
+    </para>
+  </section>
+  <section xml:id="new-services">
+    <title>New Services</title>
+    <para>
+    </para>
+  </section>
   <section xml:id="backward-incompatibilities">
-    <title>Backward incompatibilities</title>
+    <title>Backward Incompatibilities</title>
     <itemizedlist spacing="compact">
       <listitem>
         <para>
@@ -23,4 +33,9 @@
       </listitem>
     </itemizedlist>
   </section>
+  <section xml:id="other-notable-changes">
+    <title>Other Notable Changes</title>
+    <para>
+    </para>
+  </section>
 </section>

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

@@ -4,6 +4,12 @@ In addition to numerous new and upgraded packages, this release has the followin
 
 * Support is planned until the end of April 2022, handing over to 22.05.
 
-## Backward incompatibilities
+## Highlights
+
+## New Services
+
+## Backward Incompatibilities
 
 * The `staticjinja` package has been upgraded from 1.0.4 to 2.0.0
+
+## Other Notable Changes