Add Chrome extension to the Chrome browser in NodeJS + Selenium

ChromeOptions_ChromeExtension.js

var webdriver = require('selenium-webdriver');
var chrome = require("selenium-webdriver/chrome");
var fs = require('fs');

let file_path = '/Users/test/Downloads/Page Ruler.crx';
let buff = new Buffer.from(fs.readFileSync(file_path));
let base64data = buff.toString('base64');

var capabilities = {

	'project' : 'Test Run',
	'build' : 'Build v1',
	'name' : 'Chrome Extensions',

  'browserName' : 'Chrome',
  'os' : 'Windows',
  'os_version' : '10',
  
  'browserstack.debug' : 'true',
  'browserstack.user' : '<BROWSERSTACK_USERNAME>',
  'browserstack.key' : '<BROWSERSTACK_ACCESS_KEY>',
  
  'chromeOptions': { 
    'extensions' : [ base64data ]
  }
}

var driver = new webdriver.Builder().
  usingServer('http://hub-usw.browserstack.com/wd/hub').
  withCapabilities(capabilities).
  build();

driver.get('https://the-internet.herokuapp.com/login').then(function(){
  driver.findElement(webdriver.By.xpath('.//button[@type="submit"]')).click().then(function(){
    driver.getTitle().then(function(title) {
      console.log(title);
      driver.quit();
    });
  });
});