增加备用地址

sa-token-doc/doc/index.html

@@ -160,13 +160,20 @@
 		<script src="lib/docsify-tabs.min.js"></script>
 		<!-- img点击放大 -->
 		<script src="lib/zoom-image.min.js"></script>
-		
+
 		<!-- sidebar折叠 -->
 		<!-- <link rel="stylesheet" href="//cdn.jsdelivr.net/npm/docsify-sidebar-collapse/dist/sidebar.min.css" />
 		<script src="//cdn.jsdelivr.net/npm/docsify-sidebar-collapse/dist/docsify-sidebar-collapse.min.js"></script> -->
 
 		<!-- jqeury -->
 		<script src="https://unpkg.zhimg.com/jquery@3.4.1/dist/jquery.min.js"></script>
+		
+		<script>
+			if(window.jQuery === undefined) {
+				var str = 'CDN 加载失败，请打开备用地址：<a href="index-backup.html" target="_blank">index-backup.html</a>';
+				document.querySelector('#app').innerHTML = str;
+			}
+		</script>
 
 		<!-- 搜索引擎自动提交 -->
 		<script>