Adds initial intermediate qt6 porting state

qt6-after/qt6-migrated-legatus/Lts/Common/PluginInterfaces/style_plugin_interface.h

@@ -0,0 +1,22 @@
+
+
+
+#pragma once
+
+#include <QObject>
+
+namespace StylePlugin
+{
+class Plugin
+{
+public:
+  Plugin() = default;
+  virtual ~Plugin() = default;
+
+  virtual void loadStyle(bool highDpi) = 0;
+  virtual void unloadStyle() = 0;
+};
+
+} 
+
+Q_DECLARE_INTERFACE(StylePlugin::Plugin, "style")