Avalonia UI -> 11.0.0 Preview 8

[josephmoresena]

• Fix #31.
• Fix restoring main window size when changing theme.
• Fix restoring main window position when changing theme on MS Windows.
• Menu improvements.

[teobugslayer]

I am slightly concerned that in rd.xml we are taking the entire assembly, but I think in this case (a getting started tutorial), taking a conservative approach is acceptable.

Thanks for the PR!

[josephmoresena]

Avalonia 11 is much more AOT friendly than Avalonia 0.10, but in this case we need rd.xml just for the issue in windows position, now we need to get a property by reflection from the native windows instance on Windows OS in order to get the hidden border and offset the actual position of the new window when a Fluent/Simple theme switch occurs.

For macOS there is a cheaper solution, but I think the Avalonia UI should handle this problem itself. I have reported it to AvaloniaUI/Avalonia#11333 Once it is fixed we may no longer need rd.xml.

[Sayayaya]

getting this everywhere after going from 0.1x to 11.x and it's about as clear as coal as how we developers are supposed to resolve it