Merge pull request #312 from windows-toolkit/marb2000-patch-1

Update readme.md

readme.md

@@ -11,6 +11,15 @@ This repository contains all controls for WPF and WinForms to simplify and demon
 
 For everything else in the Windows Community Toolkit (UWP controls, .NET Standard web services, helpers and more), [start here](https://github.com/windows-toolkit/WindowsCommunityToolkit)
 
+## XAML Islands Notice
+The set of WPF and WinForms controls found here are _only designed to work with .NET Core 3.1_, **not** .NET 5 and above. These controls are using the XAML Islands Windows 10 APIs included within the Windows 10 OS which won't be improved anymore. 
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+WinUI 3's XAML Islands is the path forward to these .NET apps that want to use .NET 5 and WinUI. WinUI 3's XAML Islands are still in development, and we recommend reviewing the [WinUI 3 roadmap](https://github.com/Microsoft/microsoft-ui-xaml/blob/master/docs/roadmap.md) to get the latest updates. This repository will be archived once WinUI 3's XAML Islands is released.
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+In the meantime, we suggest you investigate WinUI 3 Desktop as a solution to access Win32 APIs while using the latest native UX platform. See [here](https://aka.ms/winui3) for more details.
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 ## Build Status
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