Enable embed untracked sources (#2471)

Author: JamesNK

Src/Newtonsoft.Json/Newtonsoft.Json.csproj

@@ -31,6 +31,7 @@
     <IncludeSymbols>true</IncludeSymbols>
     <SymbolPackageFormat>snupkg</SymbolPackageFormat>
     <CodeAnalysisRuleset>Newtonsoft.Json.ruleset</CodeAnalysisRuleset>
+    <EmbedUntrackedSources>true</EmbedUntrackedSources>
   </PropertyGroup>
   <ItemGroup>
     <None Remove="**\*.orig" />