Update Readme to include supported platforms (#208)

* Update Readme to include supported platforms

* Update README.md

README.md

@@ -15,9 +15,14 @@ For information on how to use this library, please refer to the relevant Quickst
 
 and also to our [docs for this library](https://auth0.github.io/auth0-oidc-client-net/documentation/intro.html).
 
+For a list of supported platforms, please refer to the relevant documentation from Microsoft:
+
+* [Xamarin](https://docs.microsoft.com/en-us/xamarin/get-started/supported-platforms)
+* [UWP/WPF/WinForms](https://docs.microsoft.com/en-us/lifecycle/faq/windows)
+
 ## Breaking changes in v3
 
 Version 3 of this library includes many potential breaking changes depending on your usage. Please read [Migrating to Auth0-OIDC-Client-NET v3](https://auth0.github.io/auth0-oidc-client-net/documentation/migration/v3.html).
 
 ## License
-[![FOSSA Status](https://app.fossa.com/api/projects/git%2Bgithub.com%2Fauth0%2Fauth0-oidc-client-net.svg?type=large)](https://app.fossa.com/projects/git%2Bgithub.com%2Fauth0%2Fauth0-oidc-client-net?ref=badge_large)
+[![FOSSA Status](https://app.fossa.com/api/projects/git%2Bgithub.com%2Fauth0%2Fauth0-oidc-client-net.svg?type=large)](https://app.fossa.com/projects/git%2Bgithub.com%2Fauth0%2Fauth0-oidc-client-net?ref=badge_large)