[libadwaita/wip/cdavis/prefs-group-buildable-docs] preferencesgroup: Document GtkBuildable behavior

[Christopher Davis <christopherdavis src gnome org>]

commit 2ff41aa051fb7f890ee6a34c346e3696f65c34fc
Author: Christopher Davis <christopherdavis gnome org>
Date:   Fri Dec 24 15:15:21 2021 -0800

    preferencesgroup: Document GtkBuildable behavior

 src/adw-preferences-group.c | 6 ++++++
 1 file changed, 6 insertions(+)
---
diff --git a/src/adw-preferences-group.c b/src/adw-preferences-group.c
index 2290e863..320ea0b3 100644
--- a/src/adw-preferences-group.c
+++ b/src/adw-preferences-group.c
@@ -29,6 +29,12 @@
  * title and a description. The title will be used by
  * [class@Adw.PreferencesWindow] to let the user look for a preference.
  *
+ * ## AdwPreferencesGroup as GtkBuildable
+ *
+ * The `AdwPreferencesGroup` implementation of the [iface@Gtk.Buildable] interface
+ * will add [class@PreferencesRow]s to the group's list. If a child is not a
+ * [class@PreferencesRow] the child is added to a box below the list.
+ *
  * ## CSS nodes
  *
  * `AdwPreferencesGroup` has a single CSS node with name `preferencesgroup`.