IPv6 Support

• Support to IPv6 (Issue #214)

You can setup IPv6 in two ways:

Using new EndPointManager.UseIpv6 will set IPAddress.IPv6Any for * hostname:

EndPointManager.UseIpv6 = true;
var instance = new WebServer("http://*:8877");

Or directly using the IPv6 address like the lookback:

var instance = new WebServer("http://[::1]:8877");

• Fix WebSocket client for targets NET47 and NETCOREAPP21
• Remove Task.Delay from polling (Issue #155)
• Add ConfigureAwait(false) to async invocations.