Added Diagnostics skoke test project

Author: Sergio0694

SmokeTests/Microsoft.Toolkit.Diagnostics/MainPage.xaml

@@ -0,0 +1,18 @@
+<Page
+    x:Class="SmokeTest.MainPage"
+    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    xmlns:local="using:SmokeTest"
+    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+    mc:Ignorable="d"
+    Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
+
+    <Grid>
+        <StackPanel HorizontalAlignment="Center" VerticalAlignment="Center" Width="200">
+            <TextBox x:Name="textBox" Text="text"/>
+            <Button Content="Is not null or empty?" Click="Button_Click" HorizontalAlignment="Center"/>
+            <TextBlock x:Name="textBlock"/>
+        </StackPanel>
+    </Grid>
+</Page>

SmokeTests/Microsoft.Toolkit.Diagnostics/MainPage.xaml.cs

@@ -0,0 +1,23 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Toolkit.Diagnostics;
+
+namespace SmokeTest
+{
+    public sealed partial class MainPage
+    {
+        public MainPage()
+        {
+            InitializeComponent();
+        }
+
+        private void Button_Click(object sender, Windows.UI.Xaml.RoutedEventArgs e)
+        {
+            Guard.IsNotNullOrEmpty(textBox.Text, nameof(textBox));
+
+            textBlock.Text = "Ok";
+        }
+    }
+}

SmokeTests/SmokeTests.proj

@@ -7,6 +7,7 @@
     <ToolkitPackages>
       UWPBaseline;
       Microsoft.Toolkit;
+      Microsoft.Toolkit.Diagnostics;
       Microsoft.Toolkit.HighPerformance;
       Microsoft.Toolkit.Mvvm;
       Microsoft.Toolkit.Parsers;