Feature enable Net 8.0 on WinUI (#3701)

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**What kind of change does this PR introduce?**
<!-- Bug fix, feature, docs update, ... -->

Feature

**What is the current behavior?**
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WinUI has net 6.0 and net 7.0 builds

**What is the new behavior?**
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ReacitveUI.WinUI now includes a build for net 8.0

**What might this PR break?**

Target framework needs to be updated to windows10.0.19041.0 if using an
earlier version.

**Please check if the PR fulfills these requirements**
- [ ] Tests for the changes have been added (for bug fixes / features)
- [ ] Docs have been added / updated (for bug fixes / features)

**Other information**:

Author: ChrisPulman

src/ReactiveUI.WinUI/ReactiveUI.WinUI.csproj

@@ -1,17 +1,19 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>net6.0-windows10.0.17763.0;net7.0-windows10.0.17763.0</TargetFrameworks>
-    <TargetPlatformMinVersion>10.0.17763.0</TargetPlatformMinVersion>
+    <TargetFrameworks>net6.0-windows10.0.19041.0;net7.0-windows10.0.19041.0;net8.0-windows10.0.19041.0</TargetFrameworks>
+    <TargetPlatformMinVersion>10.0.19041.0</TargetPlatformMinVersion>
     <PackageDescription>Contains the ReactiveUI platform specific extensions for WinUI Desktop</PackageDescription>
     <RootNamespace>ReactiveUI.WinUI.Desktop</RootNamespace>
     <PackageTags>mvvm;reactiveui;rx;reactive extensions;observable;LINQ;events;winui</PackageTags>
     <UseWinUI>true</UseWinUI>
     <DefineConstants>IS_WINUI;WINUI_TARGET;</DefineConstants>
-    <SupportedOSPlatformVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'windows'">10.0.17763.0</SupportedOSPlatformVersion>
-    <TargetPlatformMinVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'windows'">10.0.17763.0</TargetPlatformMinVersion>
+    <RuntimeIdentifiers>win-x64;win-x86;win-arm64</RuntimeIdentifiers>
+    <SupportedOSPlatformVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'windows'">10.0.19041.0</SupportedOSPlatformVersion>
+    <TargetPlatformMinVersion Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'windows'">10.0.19041.0</TargetPlatformMinVersion>
   </PropertyGroup>
 
   <ItemGroup>
+    <PackageReference Include="Microsoft.Windows.SDK.BuildTools" Version="10.0.22621.2428" />
     <PackageReference Include="Microsoft.WindowsAppSDK" Version="1.4.231115000" />
   </ItemGroup>