Upgrade newtonsoft.json to 13.0.1 to fix CG alert (#645)

Directory.Build.props

@@ -9,5 +9,6 @@
     <NuGetVersionSharpZipLib>1.3.3</NuGetVersionSharpZipLib>
     <NuGetVersionSystemConfigurationConfigurationManager>6.0.0</NuGetVersionSystemConfigurationConfigurationManager>
     <NuGetVersionLuceneDotNet>3.0.3</NuGetVersionLuceneDotNet>
+    <NuGetVersionNewtonsoftJson>13.0.1</NuGetVersionNewtonsoftJson>
   </PropertyGroup>
 </Project>

mdoc/mdoc.Test/mdoc.Test.csproj

@@ -40,6 +40,7 @@
 
   <ItemGroup>
     <PackageReference Include="Mono.Cecil" Version="$(NuGetVersionMonoCecil)" />
+    <PackageReference Include="Newtonsoft.Json" Version="$(NuGetVersionNewtonsoftJson)" />
     <PackageReference Include="NUnit" Version="$(NuGetVersionNUnit)" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="$(NuGetVersionMicrosoftNETTestSdk)" />
     <PackageReference Include="NUnit3TestAdapter" Version="$(NuGetVersionNUnit3TestAdapter)" />