Add CommandApp unit testing example (#2)

* Added console interactivity test
* Added `Should_Render_Panel` test

examples/Cli/Testing/ConsoleTests.cs

@@ -0,0 +1,43 @@
+using Spectre.Console;
+using Spectre.Console.Testing;
+
+namespace Testing;
+
+[TestClass]
+public class ConsoleTests
+{
+    [TestMethod]
+    public void Should_Render_Panel()
+    {
+        // Given
+        var console = new TestConsole();
+
+        // When
+        console.Write(new Panel(new Text("Hello World")));
+
+        // Then
+        Assert.AreEqual(console.Output, """"
+┌─────────────┐
+│ Hello World │
+└─────────────┘
+
+"""");
+    }
+
+    [TestMethod]
+    public void Should_Select_Orange()
+    {
+        // Given
+        var console = new TestConsole();
+        console.Input.PushTextWithEnter("Orange");
+
+        // When
+        console.Prompt(
+            new TextPrompt<string>("Favorite fruit?")
+                .AddChoice("Banana")
+                .AddChoice("Orange"));
+
+        // Then
+        Assert.AreEqual(console.Output, "Favorite fruit? [Banana/Orange]: Orange\n");
+    }
+}