chore: extend linting of code blocks in the docs (#40245)

* chore: extend linting of code blocks in the docs

* chore: combine lint:markdownlint and lint:markdown scripts

docs/tutorial/offscreen-rendering.md

@@ -39,22 +39,44 @@ To enable this mode, GPU acceleration has to be disabled by calling the
 
 ## Example
 
-```javascript fiddle='docs/fiddles/features/offscreen-rendering'
-const { app, BrowserWindow } = require('electron')
+```fiddle docs/fiddles/features/offscreen-rendering
+const { app, BrowserWindow } = require('electron/main')
 const fs = require('node:fs')
+const path = require('node:path')
 
 app.disableHardwareAcceleration()
 
-let win
-
-app.whenReady().then(() => {
-  win = new BrowserWindow({ webPreferences: { offscreen: true } })
+function createWindow () {
+  const win = new BrowserWindow({
+    width: 800,
+    height: 600,
+    webPreferences: {
+      offscreen: true
+    }
+  })
 
   win.loadURL('https://github.com')
   win.webContents.on('paint', (event, dirty, image) => {
     fs.writeFileSync('ex.png', image.toPNG())
   })
   win.webContents.setFrameRate(60)
+  console.log(`The screenshot has been successfully saved to ${path.join(process.cwd(), 'ex.png')}`)
+}
+
+app.whenReady().then(() => {
+  createWindow()
+
+  app.on('activate', () => {
+    if (BrowserWindow.getAllWindows().length === 0) {
+      createWindow()
+    }
+  })
+})
+
+app.on('window-all-closed', () => {
+  if (process.platform !== 'darwin') {
+    app.quit()
+  }
 })
 ```