[gnome-shell] st: Add missing include

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit de6512be1a7da4e12748c6980776571bce37a8fd
Author: Florian Müllner <fmuellner gnome org>
Date:   Mon Apr 8 18:10:00 2019 +0200

    st: Add missing include
    
    https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/485

 src/st/st-settings.h | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/src/st/st-settings.h b/src/st/st-settings.h
index 106000168..c2c4fa23e 100644
--- a/src/st/st-settings.h
+++ b/src/st/st-settings.h
@@ -24,6 +24,8 @@
 #ifndef __ST_SETTINGS_H__
 #define __ST_SETTINGS_H__
 
+#include <glib-object.h>
+
 G_BEGIN_DECLS
 
 #define ST_TYPE_SETTINGS (st_settings_get_type ())