Add links for WinUI and WindowsAppSDK in welcome.md (#49707)

Author: weitzhandler

docs/welcome.md

@@ -57,11 +57,14 @@ This documentation is completely [open source](https://github.com/dotnet/docs).
 - [.NET runtime](https://github.com/dotnet/runtime)
 - [.NET SDK](https://github.com/dotnet/sdk)
 - [.NET extensions](https://github.com/dotnet/extensions)
+- [ASP.NET Core](https://github.com/dotnet/aspnetcore)
 - [Aspire](https://github.com/dotnet/aspire)
 - [Roslyn (C# and Visual Basic) Compiler Platform and IDE Tools](https://github.com/dotnet/roslyn)
 - [.NET code analyzers](https://github.com/dotnet/roslyn-analyzers)
 - [F# Compiler and IDE Tools](https://github.com/dotnet/fsharp)
 - [Windows Forms](https://github.com/dotnet/winforms)
 - [WPF](https://github.com/dotnet/wpf)
+- [WinUI](https://github.com/microsoft/microsoft-ui-xaml)
+- [WindowsAppSDK](https://github.com/microsoft/WindowsAppSDK)
 
 You can join other people who are already active in the [.NET community](https://dotnet.microsoft.com/platform/community) to find out what's new or ask for help.