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/ListToolsRequestParams.cs

@@ -0,0 +1,15 @@
+namespace McpDotNet.Protocol.Types;
+
+/// <summary>
+/// Sent from the client to request a list of tools the server has.
+/// <see href="https://github.com/modelcontextprotocol/specification/blob/main/schema/2024-11-05/schema.json">See the schema for details</see>
+/// </summary>
+public class ListToolsRequestParams
+{
+    /// <summary>
+    /// An opaque token representing the current pagination position.
+    /// If provided, the server should return results starting after this cursor.
+    /// </summary>
+    [System.Text.Json.Serialization.JsonPropertyName("cursor")]
+    public string? Cursor { get; init; }
+}