Update CI pipeline

update Visual Studio version to 16
move CI pipeline to .pipelines folder

.pipelines/ci/templates/build-powertoys-steps.yml

@@ -0,0 +1,35 @@
+parameters:
+  additionalBuildArguments: ''
+
+steps:
+- checkout: self
+  submodules: true
+  clean: true
+
+- task: NuGetToolInstaller@0
+  displayName: Ensure NuGet 4.8.1
+  inputs:
+    versionSpec: 4.8.1
+
+- task: VisualStudioTestPlatformInstaller@1
+  displayName: Ensure VSTest Platform
+
+- task: NuGetCommand@2
+  displayName: Restore NuGet packages
+  inputs:
+    command: restore
+    feedsToUse: config
+    configPath: NuGet.config
+    restoreSolution: PowerToys.sln
+    restoreDirectory: '$(Build.SourcesDirectory)\packages'
+
+- task: VSBuild@1
+  displayName: 'Build solution **\PowerToys.sln'
+  inputs:
+    solution: '**\PowerToys.sln'
+    vsVersion: 16.0
+    platform: '$(BuildPlatform)'
+    configuration: '$(BuildConfiguration)'
+    msbuildArgs: ${{ parameters.additionalBuildArguments }}
+    clean: true
+    maximumCpuCount: true