Consider shipping System.Xaml as a separate netstandard package

[ryalanms]

System.Xaml can be used independently of WPF, but consuming System.Xaml requires building with the Windows-specific net6.0-windows target framework. Consider shipping System.Xaml as a separate netstandard package that can be built without the Windows-specific TFM.

[lindexi]

Yeah, and I made it as a separate package in https://github.com/lindexi/lindexi_gd/tree/master/System.Xaml

[lindexi]

@ryalanms Because System.Xaml depends on System.Windows.Extensions, I cannot change it to netstandard. See #4252

[lindexi]

See #3543

[AArnott]

Looks like a dupe of #46

[pchaurasia14]

Closing as duplicate.