Include README.md in NuGet package as package readme

Add PackageReadmeFile property and include the repository root
README.md in the NuGet package so NuGet.org displays the full
README content instead of only the short Description text.

Agent-Logs-Url: https://github.com/IntelliTect/IntelliTect.AspNetCore.SignalR.SqlServer/sessions/d59c3ccc-f016-4f56-b384-516beffa97bb

Co-authored-by: ascott18 <5017521+ascott18@users.noreply.github.com>

Author: Copilot

src/IntelliTect.AspNetCore.SignalR.SqlServer/IntelliTect.AspNetCore.SignalR.SqlServer.csproj

@@ -3,6 +3,7 @@
 	<PropertyGroup>
 		<TargetFrameworks>net8.0;net9.0</TargetFrameworks>
 		<GenerateDocumentationFile>true</GenerateDocumentationFile>
+		<PackageReadmeFile>README.md</PackageReadmeFile>
 
 		<!-- Sourcelink: -->
 		<PublishRepositoryUrl>true</PublishRepositoryUrl>
@@ -26,4 +27,8 @@
 		<EmbeddedResource Include="**/*.sql" />
 	</ItemGroup>
 
+	<ItemGroup>
+		<None Include="../../README.md" Pack="true" PackagePath="/" />
+	</ItemGroup>
+
 </Project>