chore: replace cdn.bootcss.com to lib.baomitu.com

feat: support custom email prefix

public/index.html

@@ -4,7 +4,7 @@
   <meta charset="UTF-8">
   <meta name="keywords" content="临时邮箱,forsaken mail,disposable mail">
   <title>Forsaken Mail</title>
-  <link href="//cdn.bootcss.com/semantic-ui/2.1.7/semantic.min.css" rel="stylesheet">
+  <link href="https://lib.baomitu.com/semantic-ui/2.1.7/semantic.min.css" rel="stylesheet">
   <link rel="stylesheet" href="/css/app.css">
   <link rel="stylesheet" href="/css/prism.css">
 </head>
@@ -66,10 +66,10 @@
   </div>
 </div>
 </body>
-<script src="//cdn.bootcss.com/jquery/2.1.4/jquery.min.js"></script>
-<script src="//cdn.bootcss.com/semantic-ui/2.1.7/semantic.min.js"></script>
-<script src="//cdn.bootcss.com/socket.io/1.3.7/socket.io.min.js"></script>
-<script src="//cdn.bootcss.com/clipboard.js/1.5.5/clipboard.min.js"></script>
+<script src="https://lib.baomitu.com/jquery/2.1.4/jquery.min.js"></script>
+<script src="https://lib.baomitu.com/semantic-ui/2.1.7/semantic.min.js"></script>
+<script src="https://lib.baomitu.com/socket.io/1.3.7/socket.io.min.js"></script>
+<script src="https://lib.baomitu.com/clipboard.js/1.5.5/clipboard.min.js"></script>
 <script src="/js/app.js"></script>
 <script src="/js/prism.js"></script>
 </html>