[minor] Add JSDoc for PerMessageDeflate constructor

lib/PerMessageDeflate.js

@@ -19,18 +19,41 @@ const kBuffers = Symbol('buffers');
 const kError = Symbol('error');
 const kOwner = Symbol('owner');
 
+//
 // We limit zlib concurrency, which prevents severe memory fragmentation
 // as documented in https://github.com/nodejs/node/issues/8871#issuecomment-250915913
 // and https://github.com/websockets/ws/issues/1202
 //
-// Intentionally global; it's the global thread pool that's
-// an issue.
+// Intentionally global; it's the global thread pool that's an issue.
+//
 let zlibLimiter;
 
 /**
- * Per-message Deflate implementation.
+ * permessage-deflate implementation.
  */
 class PerMessageDeflate {
+  /**
+   * Creates a PerMessageDeflate instance.
+   *
+   * @param {Object} options Configuration options
+   * @param {Boolean} options.serverNoContextTakeover Request/accept disabling
+   *     of server context takeover
+   * @param {Boolean} options.clientNoContextTakeover Advertise/acknowledge
+   *     disabling of client context takeover
+   * @param {(Boolean|Number)} options.serverMaxWindowBits Request/confirm the
+   *     use of a custom server window size
+   * @param {(Boolean|Number)} options.clientMaxWindowBits Advertise support
+   *     for, or request, a custom client window size
+   * @param {Number} options.level The value of zlib's `level` param
+   * @param {Number} options.memLevel The value of zlib's `memLevel` param
+   * @param {Number} options.threshold Size (in bytes) below which messages
+   *     should not be compressed
+   * @param {Number} options.concurrencyLimit The number of concurrent calls to
+   *     zlib
+   * @param {Boolean} isServer Create the instance in either server or client
+   *     mode
+   * @param {Number} maxPayload The maximum allowed message length
+   */
   constructor (options, isServer, maxPayload) {
     this._maxPayload = maxPayload | 0;
     this._options = options || {};
@@ -51,6 +74,9 @@ class PerMessageDeflate {
     }
   }
 
+  /**
+   * @type {String}
+   */
   static get extensionName () {
     return 'permessage-deflate';
   }