[Docs][Navigation] Add specifics for Region based navigation with CSM

[morning4coffe-dev]

Although the Navigate with XAML page is quite similar to what is done when using CSM, I think we should mention it there as well as the syntax is a bit different and it could help the users.
--> this is a feedback from a recent discussion with a user and part of unoplatform/uno.toolkit.ui#964.

[DevTKSS]

Would you mind tell what is meant by CSM? Looked up your mentioned PR but it did not clear up for me.

@morning4coffe-dev did see you added this to your queue... I did requested some navigation related documentation, maybe you could quick check if that is somehow related and solved all in one or not? Its #2653