Add KDDockWidgets::initPlatform()

Instead of using the static variable, which is initialized before
having QApplication.

Will allow us to remove the QTimer from Platform init

src/KDDockWidgets.cpp

@@ -0,0 +1,33 @@
+/*
+  This file is part of KDDockWidgets.
+
+  SPDX-FileCopyrightText: 2019-2022 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.
+*/
+
+
+#include "KDDockWidgets.h"
+
+#include "qtwidgets/Platform_qtwidgets.h"
+#include "qtquick/Platform_qtquick.h"
+
+#include <QDebug>
+
+void KDDockWidgets::initFrontend(FrontendType type)
+{
+    if (Platform::instance())
+        return;
+
+    switch (type) {
+    case FrontendType::QtWidgets:
+        new Platform_qtwidgets();
+        break;
+    case FrontendType::QtQuick:
+        // new Platform_qtquick(); // TODOv2
+        break;
+    }
+}