Added book Xamarin Community Toolkit Succinctly (#7356)

Author: jwigert

Diff for: books/free-programming-books-langs.md

@@ -484,6 +484,7 @@ That section got so big, we decided to split it into its own file, the [BY SUBJE
 * [.NET Microservices: Architecture for Containerized .NET Applications](https://dotnet.microsoft.com/download/e-book/microservices-architecture/pdf) - Cesar de la Torre, Bill Wagner, Mike Rousos (PDF)
 * [Porting Existing ASP.NET Apps to .NET 6](https://docs.microsoft.com/en-us/dotnet/architecture/porting-existing-aspnet-apps/) - Steve "ardalis" Smith
 * [Threading in C#](http://www.albahari.com/threading/)
+* [Xamarin Community Toolkit Succinctly](https://www.syncfusion.com/succinctly-free-ebooks/xamarin-community-toolkit-succinctly) - Alessandro Del Sole
 * [Xamarin.Forms for macOS Succinctly](https://www.syncfusion.com/ebooks/xamarin_forms_for_mac_os_succinctly) - Alessandro Del Sole
 * [Xamarin.Forms Succinctly](https://www.syncfusion.com/ebooks/xamarin-forms-succinctly) - Alessandro Del Sole