Bump Newtonsoft.Json from 10.0.3 to 13.0.1 in /Structurizr.Core

Bumps [Newtonsoft.Json](https://github.com/JamesNK/Newtonsoft.Json) from 10.0.3 to 13.0.1.
- [Release notes](https://github.com/JamesNK/Newtonsoft.Json/releases)
- [Commits](JamesNK/Newtonsoft.Json@10.0.3...13.0.1)

---
updated-dependencies:
- dependency-name: Newtonsoft.Json
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

Structurizr.Core/Structurizr.Core.csproj

@@ -17,6 +17,6 @@
     <TargetFramework>netstandard2.0</TargetFramework>
   </PropertyGroup>
   <ItemGroup>
-    <PackageReference Include="Newtonsoft.Json" Version="10.0.3" />
+    <PackageReference Include="Newtonsoft.Json" Version="13.0.1" />
   </ItemGroup>
 </Project>