Updated Xamarin eBook to preview edition.

Author: davidbritch

README.md

@@ -42,7 +42,7 @@ You can download them and start reviewing these Guides/eBooks here:
 | Architecting & Developing | Containers Lifecycle & CI/CD | App patterns with Xamarin.Forms |
 | ------------ | ------------|  ------------|
 | <a href='https://aka.ms/microservicesebook'><img src="img/ebook_arch_dev_microservices_containers_cover.png"> </a> | <a href='https://aka.ms/dockerlifecycleebook'> <img src="img/ebook_containers_lifecycle.png"> </a> | <a href='https://aka.ms/xamarinpatternsebook'> <img src="img/xamarin-enterprise-patterns-ebook-cover-small.png"> </a> |
-| <sup> <a href='https://aka.ms/microservicesebook'>**Download** (Early DRAFT, still work in progress)</a> </sup>  | <sup> <a href='https://aka.ms/dockerlifecycleebook'>**Download** (First Edition from late 2016) </a>  </sup> | <sup> <a href='https://aka.ms/xamarinpatternsebook'>**Download** (Early DRAFT, still work in progress) </a>  </sup> |
+| <sup> <a href='https://aka.ms/microservicesebook'>**Download** (Early DRAFT, still work in progress)</a> </sup>  | <sup> <a href='https://aka.ms/dockerlifecycleebook'>**Download** (First Edition from late 2016) </a>  </sup> | <sup> <a href='https://aka.ms/xamarinpatternsebook'>**Download** (Preview Edition) </a>  </sup> |
 
 Send feedback to [dotnet-architecture-ebooks-feedback@service.microsoft.com](dotnet-architecture-ebooks-feedback@service.microsoft.com)
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