Add support for converting command parameters into FileInfo and DirectoryInfo (#1145)

Add support for converting command parameters that doesn't have a built-in TypeConverter but has a constructor that takes a string. For CLI apps, FileInfo and DirectoryInfo will likely be the most useful ones, but there may be others.

test/Spectre.Console.Cli.Tests/Data/Settings/HorseSettings.cs

@@ -1,7 +1,15 @@
+using System.IO;
+
 namespace Spectre.Console.Tests.Data;
 
 public class HorseSettings : MammalSettings
 {
     [CommandOption("-d|--day")]
     public DayOfWeek Day { get; set; }
+
+    [CommandOption("--file")]
+    public FileInfo File { get; set; }
+
+    [CommandOption("--directory")]
+    public DirectoryInfo Directory { get; set; }
 }