docs: virtfs: add section separators

Signed-off-by: NChristian Schoenebeck <qemu_oss@crudebyte.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>
Signed-off-by: NJán Tomko <jtomko@redhat.com>

docs/formatdomain.html.in

@@ -4084,13 +4084,20 @@
         </dd>
         </dl>
 
+      <p>
       <span class="since">Since 5.2.0</span>, the filesystem element
       has an optional attribute <code>model</code> with supported values
       "virtio-transitional", "virtio-non-transitional", or "virtio".
       See <a href="#elementsVirtioTransitional">Virtio transitional devices</a>
       for more details.
+      </p>
+
       </dd>
 
+      <p>
+      The <code>filesystem</code> element may contain the following subelements:
+      </p>
+
       <dt><code>driver</code></dt>
       <dd>
         The optional driver element allows specifying further details