Suggestion: In QDockWidget - Make docked windows able to collapse to one side and be represented by a tabbar

In QDockWidget - Make docked windows able to collapse to the side window pane of main window and be represented by a tab.

Add a minimize button to the docked window. When clicked, the docked window will collapse to one side and be represented by a tab at the side window pane of the main window. When the tab is clicked, the docked window will be retored.