Refactor GDK platform to be base for Xbox consoles

Source/Engine/Platform/GDK/GDKInput.h

@@ -0,0 +1,19 @@
+// Copyright (c) 2012-2021 Wojciech Figat. All rights reserved.
+
+#pragma once
+
+#if PLATFORM_GDK
+
+/// <summary>
+/// GDK platform specific implementation of the input system parts.
+/// </summary>
+class GDKInput
+{
+public:
+
+    static void Init();
+    static void Exit();
+    static void Update();
+};
+
+#endif