Add restore-shortcuts to key bindings list

gnome-control-center uses this to list the keybindings, without this
users cannot change the default key combo to restore shortcuts.

https://bugzilla.gnome.org/show_bug.cgi?id=789386

data/50-mutter-wayland.xml

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<KeyListEntries schema="org.gnome.mutter.wayland.keybindings"
+                group="system"
+                name="System"
+                wm_name="Mutter"
+                package="mutter">
+
+	<KeyListEntry name="restore-shortcuts" description="Restore the keyboard shortcuts"/>
+
+</KeyListEntries>

data/Makefile.am

@@ -12,6 +12,11 @@ xml_DATA = \
         50-mutter-system.xml \
         50-mutter-windows.xml
 
+if HAVE_WAYLAND
+xml_DATA += \
+        50-mutter-wayland.xml
+endif
+
 gschema_in_files = \
 	org.gnome.mutter.gschema.xml.in	\
 	org.gnome.mutter.wayland.gschema.xml.in