Subclassing Example/Docs

[cretz]

Can you provide an example or docs for extending a Qt class? E.g. A simple example that extends qt_widgets::main_window::MainWindow and overrides closeEvent? This is commonly needed to intercept closing of a window.

(I assume this is not implemented per #26, I'll just leave this open because a simple example showing this, once done, has a lot of value and it can make it clear to other users that this is not implemented yet.)

[Riateche]

Yes, this is not implemented yet, but it's a high priority task.