[libdazzle] example: add accel to example demo

[Christian Hergert <chergert src gnome org>]

commit 95f14e381aebb89ce5443c78d84d41808a2709b6
Author: Christian Hergert <chergert redhat com>
Date:   Sun Jul 9 17:32:39 2017 -0700

    example: add accel to example demo
    
    Long term we don't need this (once the labels auto update) but
    this lets us test things a bit.

 examples/app/gtk/menus.ui |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/examples/app/gtk/menus.ui b/examples/app/gtk/menus.ui
index 573de44..2448102 100644
--- a/examples/app/gtk/menus.ui
+++ b/examples/app/gtk/menus.ui
@@ -9,6 +9,7 @@
         <attribute name="verb-icon-name">preferences-desktop-keyboard-shortcuts-symbolic</attribute>
         <attribute name="label" translatable="yes">Keyboard _Shortcuts</attribute>
         <attribute name="action">app.shortcuts</attribute>
+        <attribute name="accel">&lt;control&gt;&lt;shift&gt;question</attribute>
       </item>
       <item>
         <attribute name="label" translatable="yes">_About</attribute>