Let VS add a service tag to test project

Author: AArnott

LibGit2Sharp.Tests/LibGit2Sharp.Tests.csproj

@@ -32,5 +32,8 @@
     <PackageReference Include="xunit.runner.msbuild" Version="2.2.0" Condition=" '$(TargetFramework)' == 'net46' " />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.0.0" />
   </ItemGroup>
+  <ItemGroup>
+    <Service Include="{82a7f48d-3b50-4b1e-b82e-3ada8210c358}" />
+  </ItemGroup>
   <Import Project="..\LibGit2Sharp\ExtraDefine.targets" />
 </Project>