fix: google init.

Author: lisniuse

docs/.vuepress/configs/head.js

@@ -96,14 +96,15 @@ module.exports = [
  // 谷歌统计第二段代码
  ['script', {}, `
  (function() {
- document.onreadystatechange = function() {
+ document.addEventListener('readystatechange', function (e) {
  if (document.readyState == 'complete') {
+ console.log('google init.');
  window.dataLayer = window.dataLayer || [];
  function gtag(){dataLayer.push(arguments);}
  gtag('js', new Date());
  gtag('config', 'UA-163860037-1');
  }
- }
+ });
  })();
 `],
 // 广告系统