test: add a manual test for wasm keyboard tracking

src/SamplesApp/UITests.Shared/UITests.Shared.projitems

@@ -4254,6 +4254,10 @@
       <SubType>Designer</SubType>
       <Generator>MSBuild:Compile</Generator>
     </Page>
+    <Page Include="$(MSBuildThisFileDirectory)Windows_UI_Xaml_Input\Keyboard\Keyboard_Modifiers.xaml">
+      <SubType>Designer</SubType>
+      <Generator>MSBuild:Compile</Generator>
+    </Page>
     <Page Include="$(MSBuildThisFileDirectory)Windows_UI_Xaml_Input\Keyboard\Keyboard_iOS_Theme.xaml">
       <SubType>Designer</SubType>
       <Generator>MSBuild:Compile</Generator>
@@ -8185,6 +8189,9 @@
     <Compile Include="$(MSBuildThisFileDirectory)Windows_UI_Xaml_Input\Keyboard\Keyboard_Events.xaml.cs">
       <DependentUpon>Keyboard_Events.xaml</DependentUpon>
     </Compile>
+    <Compile Include="$(MSBuildThisFileDirectory)Windows_UI_Xaml_Input\Keyboard\Keyboard_Modifiers.xaml.cs">
+      <DependentUpon>Keyboard_Modifiers.xaml</DependentUpon>
+    </Compile>
     <Compile Include="$(MSBuildThisFileDirectory)Windows_UI_Xaml_Input\Keyboard\Keyboard_iOS_Theme.xaml.cs">
       <DependentUpon>Keyboard_iOS_Theme.xaml</DependentUpon>
     </Compile>

src/SamplesApp/UITests.Shared/Windows_UI_Xaml_Input/Keyboard/Keyboard_Modifiers.xaml

@@ -0,0 +1,23 @@
+<Page
+	x:Class="UITests.Windows_UI_Xaml_Input.Keyboard.Keyboard_Modifiers"
+	xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+	xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+	xmlns:local="using:UITests.Windows_UI_Xaml_Input.Keyboard"
+	xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+	xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+	mc:Ignorable="d"
+	Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
+
+	<StackPanel>
+		<TextBlock>
+			<Run Text="Repro steps (only Uno targets, not WinUI):" />
+			<LineBreak />
+			<Run Text="1. You should see 'Modifiers pressed: None' below." />
+			<LineBreak />
+			<Run Text="2. Press the Shift key. You should see the modifier status below change to reflect that shift is pressed" />
+			<LineBreak />
+			<Run Text="3. Release the Shift key. You should see tha modifier status below go back to 'Modifiers pressed: None'" />
+		</TextBlock>
+		<TextBlock x:Name="statusTb" Text="Modifiers pressed: None" />
+	</StackPanel>
+</Page>

src/SamplesApp/UITests.Shared/Windows_UI_Xaml_Input/Keyboard/Keyboard_Modifiers.xaml.cs

@@ -0,0 +1,55 @@
+using System;
+using System.Linq;
+using Windows.System;
+using Windows.UI.Core;
+using Microsoft.UI.Xaml;
+using Microsoft.UI.Xaml.Controls;
+using Uno.UI.Samples.Controls;
+
+namespace UITests.Windows_UI_Xaml_Input.Keyboard
+{
+	[Sample("Keyboard", IsManualTest = true)]
+	public sealed partial class Keyboard_Modifiers : Page
+	{
+		private DispatcherTimer _timer;
+
+		public Keyboard_Modifiers()
+		{
+			this.InitializeComponent();
+#if HAS_UNO
+			_timer = new DispatcherTimer();
+			_timer.Interval = TimeSpan.FromMilliseconds(100);
+			_timer.Tick += (_, _) =>
+			{
+				var mods = PlatformHelpers.GetKeyboardModifiers();
+				var modString = "";
+				if (mods.HasFlag(VirtualKeyModifiers.Shift))
+				{
+					modString += " Shift";
+				}
+				if (mods.HasFlag(VirtualKeyModifiers.Control))
+				{
+					modString += " Ctrl";
+				}
+				if (mods.HasFlag(VirtualKeyModifiers.Windows))
+				{
+					modString += " Win";
+				}
+				if (mods.HasFlag(VirtualKeyModifiers.Menu))
+				{
+					modString += " Menu";
+				}
+
+				if (string.IsNullOrEmpty(modString))
+				{
+					modString = "None";
+				}
+				statusTb.Text = $"Modifiers pressed: {modString}";
+			};
+
+			Loaded += (_, _) => _timer.Start();
+			Unloaded += (_, _) => _timer.Stop();
+#endif
+		}
+	}
+}