recommendations on use/mobile-apps: info is outdated

Hello dear fsharp community.

I checked the [https://fsharp.org/use/mobile-apps/](https://fsharp.org/use/mobile-apps/):
* It features Xamarin for mobile apps, which reached End of support (May 1, 2024).
* There is also Fabulous framework. But the website is unreachable.

Right now I'm creating a mobile native app using [Avalonia UI](https://avaloniaui.net/avalonia#features). Which works on Android and support fsharp. It would be great to add it as one of the native options.

Locate the source for the use/mobile-apps page and review its Xamarin and Fabulous references. Verify the Avalonia details from the linked site, then update the recommendations so they reflect current options and include Avalonia; done when the page no longer presents outdated or unreachable choices.

Written by the indexing model from the issue text.