readme, excluded unnecessary content files

Directory.Build.props

@@ -3,6 +3,7 @@
   <PropertyGroup>
     <PhpUnitVersion Condition="$(PhpUnitVersion) == ''">9.2.6</PhpUnitVersion>
     <VersionSuffix>preview3</VersionSuffix>
+    <PackageReadmePath>$(MSBuildThisFileDirectory)README.md</PackageReadmePath>
   </PropertyGroup>
 
 </Project>

src/PHPUnit.TestAdapter/PHPUnit.TestAdapter.csproj

@@ -7,7 +7,11 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.TestPlatform.ObjectModel" Version="16.0.0" ExcludeAssets="runtime" />
-    <PackageReference Include="phpunit.phpunit" Version="$(PhpUnitVersion)-preview3" />
+    <PackageReference Include="phpunit.phpunit" Version="$(PhpUnitVersion)-preview3" IncludeAssets="compile;runtime" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <None Include="$(PackageReadmePath)" Pack="true" PackagePath="assets/readme.md" Condition=" Exists('$(PackageReadmePath)') " />
   </ItemGroup>
 
 </Project>