chore!: remove unused deps, convert to ES2015 class (#1633)

BREAKING CHANGE: when creating an `MqttClient` instance `new` is now required

.github/workflows/mqttjs-test.yml

@@ -44,6 +44,8 @@ jobs:
         DEBUG: "mqttjs"
 
     - name: Test Browser
+      if: matrix.node-version == '20.x'
+      # only run on latest node version, no reason to run on all
       timeout-minutes: 2
       run: |
         npm run browser-build

bin/pub.js

@@ -3,11 +3,10 @@
 'use strict'
 
 const mqtt = require('../')
-const pump = require('pump')
+const { pipeline, Writable } = require('readable-stream')
 const path = require('path')
 const fs = require('fs')
 const concat = require('concat-stream')
-const Writable = require('readable-stream').Writable
 const helpMe = require('help-me')({
   dir: path.join(__dirname, '..', 'doc')
 })
@@ -40,7 +39,7 @@ function multisend (args) {
   }
 
   client.on('connect', function () {
-    pump(process.stdin, split2(), sender, function (err) {
+    pipeline(process.stdin, split2(), sender, function (err) {
       client.end()
       if (err) {
         throw err