Add benchmarks

CliFx.Benchmarks/Commands/CliFxCommand.cs

@@ -0,0 +1,21 @@
+using System.Threading.Tasks;
+using CliFx.Attributes;
+using CliFx.Models;
+
+namespace CliFx.Benchmarks.Commands
+{
+    [Command]
+    public class CliFxCommand : ICommand
+    {
+        [CommandOption("str", 's')]
+        public string StrOption { get; set; }
+
+        [CommandOption("int", 'i')]
+        public int IntOption { get; set; }
+
+        [CommandOption("bool", 'b')]
+        public bool BoolOption { get; set; }
+
+        public Task ExecuteAsync(CommandContext context) => Task.CompletedTask;
+    }
+}