fix: add README.md to NuGet package for PackageReadmeFile

- Add <None> Include for README.md to pack into NuGet package
- Required by <PackageReadmeFile> metadata

Co-Authored-By: Claude <noreply@anthropic.com>

Author: JusterZhu

src/GeneralUpdate.Maui.Android/GeneralUpdate.Maui.Android.csproj

@@ -17,6 +17,10 @@
       <Pack>True</Pack>
       <PackagePath>\</PackagePath>
     </None>
+    <None Include="../../README.md">
+      <Pack>True</Pack>
+      <PackagePath>\</PackagePath>
+    </None>
   </ItemGroup>
 
   <ItemGroup>