Added simple Iris test app

Tests/SimpleIrisApp/Pages/MainPage.uix

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+<?xml version="1.0" encoding="utf-8" ?>
+<UIX xmlns="http://schemas.microsoft.com/2007/uix">
+    <UI Name="Frame">
+        <Content>
+            <Panel Layout="VerticalFlow">
+                <Children>
+                    <Graphic Content="clr-res://SimpleIrisApp!ZuneDevLogo.png" StretchingPolicy="Uniform"
+                             SizingPolicy="SizeToContent" MaximumSize="140,0"/>
+
+                    <Text Content="Howdy from Microsoft Iris!" Font="Segoe UI,14" Color="White"/>
+                </Children>
+            </Panel>
+        </Content>
+    </UI>
+</UIX>

Tests/SimpleIrisApp/Program.cs

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+using Microsoft.Iris;
+using System;
+using System.IO;
+
+namespace SimpleIrisApp;
+
+internal class Program
+{
+    static void Main(string[] args)
+    {
+        Console.WriteLine("Launching Iris app...");
+
+        Application.Initialize();
+
+        Application.Window.Caption = "Iris app";
+        Application.Window.RequestLoad("clr-res://SimpleIrisApp!MainPage.uix#Frame");
+
+        Application.Run(OnInitialLoadComplete);
+    }
+
+    static void OnInitialLoadComplete(object arg)
+    {
+        Console.WriteLine("Initial load complete");
+    }
+}

Tests/SimpleIrisApp/SimpleIrisApp.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <OutputType>Exe</OutputType>
+        <TargetFramework>net6.0</TargetFramework>
+        <Nullable>enable</Nullable>
+        <Platforms>x86;x64</Platforms>
+    </PropertyGroup>
+
+    <ItemGroup>
+        <EmbeddedResource Include="Assets\*.*" />
+        <EmbeddedResource Include="Pages\*.*" />
+    </ItemGroup>
+
+    <ItemGroup>
+        <ProjectReference Include="..\..\UIX\UIX.csproj" />
+    </ItemGroup>
+
+    <Target Name="CopyCustomContent" AfterTargets="AfterBuild">
+        <Copy SourceFiles="..\..\UIXrender.dll" DestinationFolder="$(OutDir)" />
+    </Target>
+
+</Project>