[gtk] docs: Regroup the tree support parts

[Matthias Clasen <matthiasc src gnome org>]

commit 9f335d3ee6cbbaed89e5a2aa5c245f2fb8971e47
Author: Matthias Clasen <mclasen redhat com>
Date:   Sat Jun 6 13:29:55 2020 -0400

    docs: Regroup the tree support parts
    
    Give the chapter a title, and put some things in sections.

 docs/reference/gtk/gtk4-docs.xml | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
---
diff --git a/docs/reference/gtk/gtk4-docs.xml b/docs/reference/gtk/gtk4-docs.xml
index 2f8924b313..247e166eb8 100644
--- a/docs/reference/gtk/gtk4-docs.xml
+++ b/docs/reference/gtk/gtk4-docs.xml
@@ -94,8 +94,11 @@
     </chapter>
 
     <chapter id="Trees">
-      <xi:include href="xml/gtktreelistrow.xml" />
+      <title>Tree support</title>
       <xi:include href="xml/gtktreelistmodel.xml" />
+      <section>
+        <xi:include href="xml/gtktreelistrow.xml" />
+      </section>
       <xi:include href="xml/gtktreelistrowsorter.xml" />
       <xi:include href="xml/gtktreeexpander.xml" />
     </chapter>