[Doc] ContentDialog documentation needs improvements

[agneszitte]

On which page?

https://platform.uno/docs/articles/controls/ContentDialog.html

What's wrong?

ContentDialog documentation needs improvements based on the feedback received on Discord here

Key Points from the feedback:

• Lack of Examples: There are no clear examples or documentation on how to open a ContentDialog with a Command using C# Markup and MVUX. Current examples focus primarily on XAML or are too specific to other contexts (like the Counter tutorial).
• Access to XamlRoot: How to access XamlRoot in scenarios where the command is located in the "MainModel", which does not have access to XamlRoot property.

Suggested Improvements:

• Detailed Examples: Add comprehensive examples showing the use of C# Markup and MVUX/MVVM for opening ContentDialogs. Would be best to use Tabs in the documentation in order to showcase the different possibilities ([XAML][C# Markup] & [MVUX][MVVM])
• Add details pointing to the usage of Uno's Navigation Extensions documentation here, where there is the NavigationService with all the abstractions needed to inject the navigation service into the model.

[MartinZikmund]

I recently made this doc,https://github.com/unoplatform/uno/blob/master/doc/articles/features/dialogs.md , so it seems we now have similar information in two places, probably the existing info in the controls one should be moved to features doc