Capture Xunit20 output

TestOutputHelper

public static class TestOutputHelper
{
    private static readonly AsyncLocal<ITestOutputHelper> CurrentTestOutputHelper
        = new AsyncLocal<ITestOutputHelper>();

    public static void Capture(this ITestOutputHelper outputHelper)
    {
        CurrentTestOutputHelper.Value = outputHelper;
    }

    public static ITestOutputHelper Current => CurrentTestOutputHelper.Value;
}