[minor] Export the PerMessageDeflate class and header utils

Export the `PerMessageDeflate` class, the parser and serializer for the
`Sec-WebSocket-Extensions` header, and the parser for the
`Sec-WebSocket-Protocol` header.

Documentation is intentionally omitted as these utilities are primarily
intended for niche use cases rather than general consumption.

Refs: https://github.com/websockets/ws/pull/2313

index.js

@@ -1,13 +1,22 @@
 'use strict';
 
+const createWebSocketStream = require('./lib/stream');
+const extension = require('./lib/extension');
+const PerMessageDeflate = require('./lib/permessage-deflate');
+const Receiver = require('./lib/receiver');
+const Sender = require('./lib/sender');
+const subprotocol = require('./lib/subprotocol');
 const WebSocket = require('./lib/websocket');
+const WebSocketServer = require('./lib/websocket-server');
 
-WebSocket.createWebSocketStream = require('./lib/stream');
-WebSocket.Server = require('./lib/websocket-server');
-WebSocket.Receiver = require('./lib/receiver');
-WebSocket.Sender = require('./lib/sender');
-
+WebSocket.createWebSocketStream = createWebSocketStream;
+WebSocket.extension = extension;
+WebSocket.PerMessageDeflate = PerMessageDeflate;
+WebSocket.Receiver = Receiver;
+WebSocket.Sender = Sender;
+WebSocket.Server = WebSocketServer;
+WebSocket.subprotocol = subprotocol;
 WebSocket.WebSocket = WebSocket;
-WebSocket.WebSocketServer = WebSocket.Server;
+WebSocket.WebSocketServer = WebSocketServer;
 
 module.exports = WebSocket;

wrapper.mjs

@@ -1,8 +1,21 @@
 import createWebSocketStream from './lib/stream.js';
+import extension from './lib/extension.js';
+import PerMessageDeflate from './lib/permessage-deflate.js';
 import Receiver from './lib/receiver.js';
 import Sender from './lib/sender.js';
+import subprotocol from './lib/subprotocol.js';
 import WebSocket from './lib/websocket.js';
 import WebSocketServer from './lib/websocket-server.js';
 
-export { createWebSocketStream, Receiver, Sender, WebSocket, WebSocketServer };
+export {
+  createWebSocketStream,
+  extension,
+  PerMessageDeflate,
+  Receiver,
+  Sender,
+  subprotocol,
+  WebSocket,
+  WebSocketServer
+};
+
 export default WebSocket;