Add MapResult example to HelpText Configuration Wiki

Please add the following example to the https://github.com/commandlineparser/commandline/wiki/HelpText-Configuration page.

```
class Program {
static int Main(string[] args) {
var parserResult = new Parser(c => c.HelpWriter = null).ParseArguments(args);
return parserResult.MapResult(
(Options opts) => new Run(opts),
errs => DisplayHelp(parserResult, errs)
);
}

static int DisplayHelp(ParserResult parserResult, IEnumerable errs) {
Console.WriteLine(HelpText.AutoBuild(parserResult, h => {
h.AddPreOptionsLine(Environment.NewLine + "Use this tool wisely!");
return h;
}));
return 1;
}
}
```

Also I had a great trouble finding this page, please add more links to it.