Add Packages section to ModelContextProtocol README with absolute documentation URLs

Co-authored-by: jeffhandley <1031940+jeffhandley@users.noreply.github.com>

Author: Copilot

src/ModelContextProtocol/README.md

@@ -4,6 +4,16 @@
 
 The official C# SDK for the [Model Context Protocol](https://modelcontextprotocol.io/), with hosting and dependency injection extensions. References `ModelContextProtocol.Core`. Please visit the [API documentation](https://modelcontextprotocol.github.io/csharp-sdk/api/ModelContextProtocol.html) for more details on available functionality.
 
+## Packages
+
+This SDK consists of three main packages:
+
+- **[ModelContextProtocol.Core](https://www.nuget.org/packages/ModelContextProtocol.Core)** [![NuGet version](https://img.shields.io/nuget/v/ModelContextProtocol.Core.svg)](https://www.nuget.org/packages/ModelContextProtocol.Core) - For projects that only need to use the client or low-level server APIs and want the minimum number of dependencies. [Documentation](https://modelcontextprotocol.github.io/csharp-sdk/api/ModelContextProtocol.html)
+
+- **[ModelContextProtocol](https://www.nuget.org/packages/ModelContextProtocol)** [![NuGet version](https://img.shields.io/nuget/v/ModelContextProtocol.svg)](https://www.nuget.org/packages/ModelContextProtocol) - The main package with hosting and dependency injection extensions. References `ModelContextProtocol.Core`. This is the right fit for most projects that don't need HTTP server capabilities. [Documentation](https://modelcontextprotocol.github.io/csharp-sdk/api/ModelContextProtocol.html)
+
+- **[ModelContextProtocol.AspNetCore](https://www.nuget.org/packages/ModelContextProtocol.AspNetCore)** [![NuGet version](https://img.shields.io/nuget/v/ModelContextProtocol.AspNetCore.svg)](https://www.nuget.org/packages/ModelContextProtocol.AspNetCore) - The library for HTTP-based MCP servers. References `ModelContextProtocol`. [Documentation](https://modelcontextprotocol.github.io/csharp-sdk/api/ModelContextProtocol.AspNetCore.html)
+
 ## Installation
 
 ```