feat: use unpkg for prism and lock version

Author: MichaelCurrin

docs/index.html

@@ -9,7 +9,7 @@
 
     <title>DocsifyJS Tutorial</title>
     <meta name="description"
-        content="A tutorial for how to build a documentation site for your Github project using DocsifyJS">
+        content="A tutorial for how to build a documentation site for your GitHub project using DocsifyJS">
 
     <link rel="icon" href="_media/docs_face.png">
 
@@ -26,7 +26,7 @@
     <script src="//unpkg.com/docsify-edit-on-github@1/index.js"></script>
 
     <script defer src="//unpkg.com/docsify@4/lib/docsify.min.js"></script>
-    <script defer src="//cdn.jsdelivr.net/npm/prismjs/components/prism-markdown.min.js"></script>
+    <script defer src="//unpkg.com/prismjs@1.28.0/components/prism-markdown.min.js"></script>
 
 </head>