Add ASP.NET Core MCP server sample to main README

[Copilot]

This PR adds a new "Getting Started (ASP.NET Core Server)" section to the main README to demonstrate how to create HTTP-based MCP servers using the ModelContextProtocol.AspNetCore package.

Changes Made

• Added a comprehensive new section following the same format as the existing "Getting Started (Server)" section
• Includes clear installation instructions using dotnet new web and the AspNetCore package
• Provides two working examples:
  1. Basic example with an echo tool (similar to the existing server example)
  2. Advanced example showing dependency injection with IHttpClientFactory
• References the detailed AspNetCore package documentation for additional information

Sample Code

The basic example shows how to set up an ASP.NET Core MCP server:

using ModelContextProtocol.Server;
using System.ComponentModel;

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddMcpServer()
    .WithHttpTransport()
    .WithToolsFromAssembly();
var app = builder.Build();

app.MapMcp();
app.Run("http://localhost:3001");

[McpServerToolType]
public static class EchoTool
{
    [McpServerTool, Description("Echoes the message back to the client.")]
    public static string Echo(string message) => $"hello {message}";
}

The advanced example demonstrates how to leverage ASP.NET Core's dependency injection system with MCP tools.

Testing

• All sample code has been validated and compiles successfully
• Created test projects to verify the examples work as documented
• Maintained consistency with existing documentation style and formatting

Fixes #14.

---

💬 Share your feedback on Copilot coding agent for the chance to win a $200 gift card! Click here to start the survey.