fix the codefund load error (#569)

official domain name is changed, which cause the issue. change to use the newest plugin.

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* [ ] Make sure you are merging your commits to `master` branch.
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Author: njleonzhang

docs/index.html

@@ -14,7 +14,7 @@
   <link rel="stylesheet" href="//unpkg.com/docsify/lib/themes/dark.css" title="dark" disabled>
   <link rel="stylesheet" href="//unpkg.com/docsify/lib/themes/buble.css" title="buble" disabled>
   <link rel="stylesheet" href="//unpkg.com/docsify/lib/themes/pure.css" title="pure" disabled>
-  <script src="//unpkg.com/docsify-plugin-codefund@1.0.3/index.js"></script>
+  <script src="//unpkg.com/docsify-plugin-codefund/index.js"></script>
   <style>
     nav.app-nav li ul {
       min-width: 100px;