XInput wrapper in a single and monolithic C# class that can be embedded as source code in any project. No external libraries, except XInput1_4.DLL but it ships today as a system component in Windows 8/8.1/10. It is available "inbox" and does not require redistribution with an application. To implement this class into your own project, just add the "X.cs" class file and start using it without any restriction. Anyway you can download latest release and add a reference to XInput.Wrapper.dll.
$ dotnet add package XInput.WrapperNo README available.