Documentation bug - Async event stream code example & adding dev source

[joantune]

The code on the AsyncStream code example should be:

 CancellationTokenSource cancellation = new CancellationTokenSource();
            Stream stream = await client.System.MonitorEventsAsync(new ContainerEventsParameters(), cancellation.Token);

I would also add the dotnet -s example to add the development version, so that we can actually navigate on the code and get proper documentation - these are perhaps more important for me as I'm a new .NET core developer (been using .NET for a while, but not the core)