worker: graduate BroadcastChannel to supported

Signed-off-by: James M Snell <jasnell@gmail.com>

PR-URL: #41271
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

doc/api/worker_threads.md

@@ -347,10 +347,12 @@ if (isMainThread) {
 
 <!-- YAML
 added: v15.4.0
+changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/00000
+    description: No longer experimental.
 -->
 
-> Stability: 1 - Experimental
-
 Instances of `BroadcastChannel` allow asynchronous one-to-many communication
 with all other `BroadcastChannel` instances bound to the same channel name.
 

lib/internal/worker/io.js

@@ -395,6 +395,9 @@ function isBroadcastChannel(value) {
 }
 
 class BroadcastChannel extends EventTarget {
+  /**
+   * @param {string} name
+   */
   constructor(name) {
     if (arguments.length === 0)
       throw new ERR_MISSING_ARGS('name');
@@ -426,12 +429,18 @@ class BroadcastChannel extends EventTarget {
     }, opts)}`;
   }
 
+  /**
+   * @type {string}
+   */
   get name() {
     if (!isBroadcastChannel(this))
       throw new ERR_INVALID_THIS('BroadcastChannel');
     return this[kName];
   }
 
+  /**
+   * @returns {void}
+   */
   close() {
     if (!isBroadcastChannel(this))
       throw new ERR_INVALID_THIS('BroadcastChannel');
@@ -445,6 +454,11 @@ class BroadcastChannel extends EventTarget {
     this[kHandle] = undefined;
   }
 
+  /**
+   *
+   * @param {*} message
+   * @returns {void}
+   */
   postMessage(message) {
     if (!isBroadcastChannel(this))
       throw new ERR_INVALID_THIS('BroadcastChannel');
@@ -460,6 +474,9 @@ class BroadcastChannel extends EventTarget {
   // BroadcastChannel API definition. Typically we shouldn't extend Web
   // Platform APIs with Node.js specific methods but ref and unref
   // are a bit special.
+  /**
+   * @returns {BroadcastChannel}
+   */
   ref() {
     if (!isBroadcastChannel(this))
       throw new ERR_INVALID_THIS('BroadcastChannel');
@@ -472,6 +489,9 @@ class BroadcastChannel extends EventTarget {
   // BroadcastChannel API definition. Typically we shouldn't extend Web
   // Platform APIs with Node.js specific methods but ref and unref
   // are a bit special.
+  /**
+   * @returns {BroadcastChannel}
+   */
   unref() {
     if (!isBroadcastChannel(this))
       throw new ERR_INVALID_THIS('BroadcastChannel');