resolving WinUI3 pipeline issues

Author: Satwik Kumar Sharma

.pipelines/winui3-ci.yml

@@ -22,7 +22,7 @@ variables:
 
 pool:
   name: Azure Pipelines
-  vmImage: windows-2019
+  vmImage: windows-2022
 
 steps:
 - task: NuGetToolInstaller@1
@@ -31,6 +31,12 @@ steps:
   inputs:
     versionSpec: 6.4.x
 
+- task: UseDotNet@2
+  displayName: 'Install .NET 8 SDK'
+  inputs:
+    version: '8.0.x'
+    packageType: 'sdk'
+
 - task: NuGetAuthenticate@1
   name: NuGetAuthenticate2