docs: update clipboard fiddles (#36946)

docs/fiddles/system/clipboard/copy/main.js

@@ -1,4 +1,5 @@
-const { app, BrowserWindow } = require('electron')
+const { app, BrowserWindow, ipcMain, clipboard } = require('electron')
+const path = require('path')
 
 let mainWindow = null
 
@@ -8,7 +9,7 @@ function createWindow () {
     height: 400,
     title: 'Clipboard copy',
     webPreferences: {
-      nodeIntegration: true
+      preload: path.join(__dirname, 'preload.js')
     }
   }
 
@@ -20,6 +21,18 @@ function createWindow () {
   })
 }
 
+ipcMain.handle('clipboard:writeText', (event, text) => {
+  clipboard.writeText(text)
+})
+
 app.whenReady().then(() => {
   createWindow()
+  
+  app.on('activate', function () {
+    if (BrowserWindow.getAllWindows().length === 0) createWindow()
+  })
+})
+
+app.on('window-all-closed', function () {
+  if (process.platform !== 'darwin') app.quit()
 })