[gnome-shell-extensions] windowsNavigator: Add missing imports

[Florian Müllner <fmuellner src gnome org>]

commit cc52f4a260fd42cde3f65207cde805051b6a6735
Author: Florian Müllner <fmuellner gnome org>
Date:   Sun Jan 26 23:05:31 2020 +0100

    windowsNavigator: Add missing imports
    
    Commit 63615cb657 missed that, which is an easy mistake to make.
    
    But how on earth did CI not catch this?!
    
    https://gitlab.gnome.org/GNOME/gnome-shell-extensions/merge_requests/104

 extensions/windowsNavigator/extension.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/extensions/windowsNavigator/extension.js b/extensions/windowsNavigator/extension.js
index 8ec9437..e359c12 100644
--- a/extensions/windowsNavigator/extension.js
+++ b/extensions/windowsNavigator/extension.js
@@ -1,6 +1,6 @@
 /* -*- mode: js2; js2-basic-offset: 4; indent-tabs-mode: nil -*- */
 /* exported init */
-const { Clutter, St } = imports.gi;
+const { Clutter, GObject, St } = imports.gi;
 
 const Main = imports.ui.main;
 const Workspace = imports.ui.workspace;