[BUG] Document how AutoDataTemplteBindingHook works on windows frameworks.

[glennawatson]

Document the fact there is a AutoDataTemplateBindingHook on windows, and how you need to either specify a ItemTemplate, DisplayMemberPath or ItemTemplateSelector if you use RxUI binding to a ItemsSource on the windows platforms.

https://github.com/reactiveui/ReactiveUI/blob/master/src/ReactiveUI/Platforms/windows-common/AutoDataTemplateBindingHook.cs

[tim-fay]

Hello @glennawatson, can you please clarify if there're any updates of documentation on how to use AutoDataTemplteBindingHook? Thanks!