Moved MainWindowBase/MainWindow into controllers/view folder

This is just the move, not ported yet

src/views_qtwidgets/ViewWrapper_qtwidgets.h

@@ -17,7 +17,6 @@
 
 namespace KDDockWidgets::Views {
 
-
 /// @brief A View that doesn't own its QWidget
 /// Implements a View API around an existing QWidget
 /// Useful for widgets that are not created by KDDW.
@@ -30,4 +29,4 @@ private:
     QWidget *const m_widget;
 };
 
-}
+}