Add application description to metadata

CliFx.Tests.Dummy/Program.cs

@@ -7,6 +7,7 @@ namespace CliFx.Tests.Dummy
         public static Task<int> Main(string[] args) =>
             new CliApplicationBuilder()
                 .WithCommandsFromThisAssembly()
+                .UseDescription("Dummy program used for E2E tests.")
                 .Build()
                 .RunAsync(args);
     }