Add Platform_qtquick

CMake hacked for now. Not sure if we should allow building
both QtWidgets and QtQuick frontends at the same time

src/qtquick/Platform_qtquick.h

@@ -0,0 +1,28 @@
+/*
+  This file is part of KDDockWidgets.
+
+  SPDX-FileCopyrightText: 2020-2022 Klarälvdalens Datakonsult AB, a KDAB Group company <info@kdab.com>
+  Author: Sérgio Martins <sergio.martins@kdab.com>
+
+  SPDX-License-Identifier: GPL-2.0-only OR GPL-3.0-only
+
+  Contact KDAB at <info@kdab.com> for commercial licensing options.
+*/
+
+#pragma once
+
+#include "Platform.h"
+
+namespace KDDockWidgets {
+
+/// @brief implements functions specific to a particular platform
+/// A platform can be for example qtwidgets, qtquick, etc.
+class DOCKS_EXPORT Platform_qtquick : public Platform
+{
+public:
+    Platform_qtquick();
+    ~Platform_qtquick() override;
+    const char *name() const override;
+};
+
+}