add debug symbols and explicit packable configuration to src/Directory.build.props

Author: matracey

src/Directory.Build.props

@@ -1,14 +1,17 @@
-<Project>
+<Project>
 
   <PropertyGroup>
     <TargetFrameworks>net8.0;net7.0;net6.0;netstandard2.0;net462</TargetFrameworks>
     <Nullable>enable</Nullable>
     <LangVersion>latest</LangVersion>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <NoWarn>$(NoWarn);CS1591</NoWarn>
+    <DebugType>Embedded</DebugType>
+    <EmbedAllSources>True</EmbedAllSources>
   </PropertyGroup>
 
   <PropertyGroup>
+    <IsPackable>true</IsPackable>
     <JsonDiffPatchPackageVersion>2.0.0</JsonDiffPatchPackageVersion>
     <Authors>Wei Chen</Authors>
     <PackageProjectUrl>https://github.com/weichch/system-text-json-jsondiffpatch</PackageProjectUrl>