Added Xamarin links (Closes #929, #606)

README.md

@@ -76,6 +76,10 @@ github "danielgindi/Charts" ~> 2.2.4
 
 In order to build the binaries for a new release, use `carthage build --no-skip-current && carthage archive Charts && carthage archive ChartsRealm`.
 
+## 3rd party bindings
+
+Xamarin (by @Flash3001): *iOS* - [GitHub](https://github.com/Flash3001/iOSCharts.Xamarin)/[NuGet](https://www.nuget.org/packages/iOSCharts/). *Android* - [GitHub](https://github.com/Flash3001/MPAndroidChart.Xamarin)/[NuGet](https://www.nuget.org/packages/MPAndroidChart/).
+
 ## Help
 
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