[gnome-desktop] docs: Add GnomeBGCrossfade and GnomeBGSlideShow

[Michael Catanzaro <mcatanzaro src gnome org>]

commit 9f29026d2f11752882b5381db35336b8e23d1c36
Author: Guido Günther <agx sigxcpu org>
Date:   Mon Dec 7 11:38:08 2020 +0100

    docs: Add GnomeBGCrossfade and GnomeBGSlideShow

 docs/reference/gnome-desktop3/gnome-desktop3-docs.sgml | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/docs/reference/gnome-desktop3/gnome-desktop3-docs.sgml 
b/docs/reference/gnome-desktop3/gnome-desktop3-docs.sgml
index e6e111e4..6a23496d 100644
--- a/docs/reference/gnome-desktop3/gnome-desktop3-docs.sgml
+++ b/docs/reference/gnome-desktop3/gnome-desktop3-docs.sgml
@@ -18,6 +18,8 @@ The libgnome-desktop library contains APIs that can be useful for a few applicat
   <part id="background">
     <title>Desktop Background</title>
     <xi:include href="xml/gnome-bg.xml"/>
+    <xi:include href="xml/gnome-bg-crossfade.xml"/>
+    <xi:include href="xml/gnome-bg-slide-show.xml"/>
   </part>
 
   <part id="randr">