Server support (stdio) (#19)

* Server support (stdio)
* TestServer project
* Refactored McpClient class to extract shared endpoint logic (with McpServer) to a base class, McpJsonRpcEndpoint.
* Improved xmldoc comments for protocol types, mirroring specification schema comments.
* Update README.MD

src/mcpdotnet/Protocol/Types/InitializeRequestParams.cs

@@ -0,0 +1,28 @@
+namespace McpDotNet.Protocol.Types;
+
+using System.Text.Json.Serialization;
+
+/// <summary>
+/// Parameters for an initialization request sent to the server.
+/// <see href="https://github.com/modelcontextprotocol/specification/blob/main/schema/2024-11-05/schema.json">See the schema for details</see>
+/// </summary>
+public record InitializeRequestParams
+{
+    /// <summary>
+    /// The version of the Model Context Protocol that the client wants to use.
+    /// </summary>
+    [JsonPropertyName("protocolVersion")]
+
+    public required string ProtocolVersion { get; init; }
+    /// <summary>
+    /// The client's capabilities.
+    /// </summary>
+    [JsonPropertyName("capabilities")]
+    public ClientCapabilities? Capabilities { get; init; }
+
+    /// <summary>
+    /// Information about the client implementation.
+    /// </summary>
+    [JsonPropertyName("clientInfo")]
+    public required Implementation ClientInfo { get; init; }
+}