Document .net native linking stuff

[glennawatson]

@worldbeater introduced reactiveui/ReactiveUI#1750

Just need to document how it works since the pack file only works on new nuget install.

[harvinders]

I too ran into this problem, however, adding a new package of ReactiveUI did not help. I am on Visual Studio 2019 (16.3). However adding following to the default.rd.xml fixed the issue. Also, note, I did not include the ReactiveUI package directly but included ReactiveUI.Fody package.

  <Library Name="ReactiveUI">
    <Assembly Name="ReactiveUI" Activate="Required All" Browse="Required All" Serialize="Required All" Dynamic="Required All" />
    <!-- See https://github.com/reactiveui/ReactiveUI/issues/1330 -->
    <Namespace Name="Windows.UI.Xaml.Controls" Dynamic="Required All" />
    <Namespace Name="Windows.UI.Xaml" Dynamic="Required All" />
    <Namespace Name="Microsoft.UI.Xaml.Controls" Dynamic="Required All" />
    <Namespace Name="Microsoft.UI.Xaml" Dynamic="Required All" />
  </Library>
</Directives>