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.

Open the HelpText Configuration wiki page linked in the issue and review its existing examples and navigation links. Add the supplied C# MapResult example and improve discoverability with additional links to the page. Done means the example and links are visible and correctly formatted on the wiki page.

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