feat: add APIs to support mojave dark modes (#14755)

* feat: add APIs to support mojave dark mode

Closes #13387

* docs: fix system-prefs typo

default_app/default_app.js

@@ -1,4 +1,4 @@
-const { app, BrowserWindow } = require('electron')
+const { app, BrowserWindow, systemPreferences } = require('electron')
 const path = require('path')
 
 let mainWindow = null
@@ -11,6 +11,10 @@ app.on('window-all-closed', () => {
 exports.load = async (appUrl) => {
   await app.whenReady()
 
+  if (process.platform === 'darwin') {
+    systemPreferences.startAppLevelAppearanceTrackingOS()
+  }
+
   const options = {
     width: 900,
     height: 600,