[dconf-editor] Add documented shortcut.

[Arnaud B. <arnaudb src gnome org>]

commit fcb896ee1025a0d537aad9ab8b06555bf1c07b9a
Author: Arnaud Bonatti <arnaud bonatti gmail com>
Date:   Wed Jan 23 12:30:27 2019 +0100

    Add documented shortcut.
    
    The <ctrl>? shortcut for the help
    overlay is so usual it is already
    documented in it; so just add it.

 editor/dconf-editor.vala | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
---
diff --git a/editor/dconf-editor.vala b/editor/dconf-editor.vala
index 97cb8e4..128d5e5 100644
--- a/editor/dconf-editor.vala
+++ b/editor/dconf-editor.vala
@@ -361,7 +361,9 @@ private class ConfigurationEditor : Gtk.Application, BaseApplication
                                                               "<Primary>KP_Enter"       });
 
      // set_accels_for_action ("app.about",                 { "<Shift><Primary>F1"      }); // TODO bug: 
needs a dance in the window
-        set_accels_for_action ("win.show-help-overlay",     {                 "F1"      }); // "<Primary>F1" 
is automatically done
+        set_accels_for_action ("win.show-help-overlay",     {                 "F1",
+                                                                     "<Primary>question",
+                                                              "<Shift><Primary>question"}); // "<Primary>F1" 
is automatically done
 
         init_night_mode ();