docs: update to the use of arrow functions in line with the style guide (#30194)

* docs: Update to the use of arrow functions in line with the style guide

* docs: Fixed unmatched bracket typo in previous commit 9ebe3e58f7948c6636d77f3c58a2693683b69691

* fix linting

Co-authored-by: Cheng Zhao <zcbenz@gmail.com>

docs/tutorial/online-offline-events.md

@@ -41,7 +41,7 @@ Starting with an HTML file `index.html`, this example will demonstrate how the `
 In order to mutate the DOM, create a `renderer.js` file that adds event listeners to the `'online'` and `'offline'` `window` events. The event handler sets the content of the `<strong id='status'>` element depending on the result of `navigator.onLine`.
 
 ```js title='renderer.js'
-function updateOnlineStatus () {
+const updateOnlineStatus = () => {
   document.getElementById('status').innerHTML = navigator.onLine ? 'online' : 'offline'
 }
 
@@ -56,7 +56,7 @@ Finally, create a `main.js` file for main process that creates the window.
 ```js title='main.js'
 const { app, BrowserWindow } = require('electron')
 
-function createWindow () {
+const createWindow = () => {
   const onlineStatusWindow = new BrowserWindow({
     width: 400,
     height: 100