docs(ShardClientUtil): link Shard#message from send method (#4028)

* docs(ShardClientUtil): link Shard#message from send method

* docs(ShardClientUtil): use @ emits instead of @ link

src/sharding/ShardClientUtil.js

@@ -79,6 +79,7 @@ class ShardClientUtil {
    * Sends a message to the master process.
    * @param {*} message Message to send
    * @returns {Promise<void>}
+   * @emits Shard#message
    */
   send(message) {
     return new Promise((resolve, reject) => {