Update README.md

Author: tom-englert

README.md

@@ -31,6 +31,7 @@ The current version supports the following features and behaviors:
 The binaries are available as [NuGet](http://nuget.org/packages/DataGridExtensions) packages.
 
 Read the [Documentation](Documentation/README.md) about how to use these features.
+The [API Documemtation](https://dotnet.github.io/DataGridExtensions/) describes the global API for DGX.
 
 Every feature is individually configurable.