fix: theme switcher in IE11 (#1502)

Author: jhildenbiddle

docs/themes.md

@@ -2,23 +2,27 @@
 
 There is a handful of themes available, both official and community-made. Copy [Vue](//vuejs.org) and [buble](//buble.surge.sh) website custom theme and [@liril-net](https://github.com/liril-net) contribution to the theme of the black style.
 
+<!-- prettier-ignore-start -->
 ```html
-<link rel="stylesheet" href="//cdn.jsdelivr.net/npm/docsify/themes/vue.css">
-<link rel="stylesheet" href="//cdn.jsdelivr.net/npm/docsify/themes/buble.css">
-<link rel="stylesheet" href="//cdn.jsdelivr.net/npm/docsify/themes/dark.css">
-<link rel="stylesheet" href="//cdn.jsdelivr.net/npm/docsify/themes/pure.css">
+<link rel="stylesheet" href="//cdn.jsdelivr.net/npm/docsify/themes/vue.css" />
+<link rel="stylesheet" href="//cdn.jsdelivr.net/npm/docsify/themes/buble.css" />
+<link rel="stylesheet" href="//cdn.jsdelivr.net/npm/docsify/themes/dark.css" />
+<link rel="stylesheet" href="//cdn.jsdelivr.net/npm/docsify/themes/pure.css" />
 ```
+<!-- prettier-ignore-end -->
 
 !> Compressed files are available in `/lib/themes/`.
 
+<!-- prettier-ignore-start -->
 ```html
 <!-- compressed -->
 
-<link rel="stylesheet" href="//cdn.jsdelivr.net/npm/docsify/lib/themes/vue.css">
-<link rel="stylesheet" href="//cdn.jsdelivr.net/npm/docsify/lib/themes/buble.css">
-<link rel="stylesheet" href="//cdn.jsdelivr.net/npm/docsify/lib/themes/dark.css">
-<link rel="stylesheet" href="//cdn.jsdelivr.net/npm/docsify/lib/themes/pure.css">
+<link rel="stylesheet" href="//cdn.jsdelivr.net/npm/docsify/lib/themes/vue.css" />
+<link rel="stylesheet" href="//cdn.jsdelivr.net/npm/docsify/lib/themes/buble.css" />
+<link rel="stylesheet" href="//cdn.jsdelivr.net/npm/docsify/lib/themes/dark.css" />
+<link rel="stylesheet" href="//cdn.jsdelivr.net/npm/docsify/lib/themes/pure.css" />
 ```
+<!-- prettier-ignore-end -->
 
 If you have any ideas or would like to develop a new theme, you are welcome to submit a [pull request](https://github.com/docsifyjs/docsify/pulls).
 
@@ -47,10 +51,10 @@ If you have any ideas or would like to develop a new theme, you are welcome to s
   var themes = Docsify.dom.findAll('[rel="stylesheet"]');
 
   preview.onclick = function (e) {
-    var title = e.target.getAttribute('data-theme')
+    var title = e.target.getAttribute('data-theme');
 
     themes.forEach(function (theme) {
-      theme.disabled = theme.title !== title
+      theme.disabled = theme.title !== title;
     });
   };
 </script>