chore: update demo js/css URLs

Signed-off-by: Jack Cherng <jfcherng@gmail.com>

Author: jfcherng

example/demo_web.php

@@ -13,8 +13,8 @@
         <title>jfcherng/php-diff - Examples</title>
 
         <!-- Prism -->
-        <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/prism/1.22.0/themes/prism-okaidia.min.css" />
-        <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/prism/1.22.0/plugins/line-numbers/prism-line-numbers.min.css" />
+        <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/prismjs@1/themes/prism-okaidia.min.css" />
+        <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/prismjs@1/plugins/line-numbers/prism-line-numbers.min.css" />
 
         <style type="text/css">
             html {
@@ -229,9 +229,9 @@
         ?>
 
         <!-- Prism -->
-        <script src="https://cdnjs.cloudflare.com/ajax/libs/prism/1.22.0/prism.min.js"></script>
-        <script src="https://cdnjs.cloudflare.com/ajax/libs/prism/1.22.0/components/prism-diff.min.js"></script>
-        <script src="https://cdnjs.cloudflare.com/ajax/libs/prism/1.22.0/components/prism-json.min.js"></script>
-        <script src="https://cdnjs.cloudflare.com/ajax/libs/prism/1.22.0/plugins/line-numbers/prism-line-numbers.min.js"></script>
+        <script src="https://cdn.jsdelivr.net/npm/prismjs@1/prism.min.js"></script>
+        <script src="https://cdn.jsdelivr.net/npm/prismjs@1/components/prism-diff.min.js"></script>
+        <script src="https://cdn.jsdelivr.net/npm/prismjs@1/components/prism-json.min.js"></script>
+        <script src="https://cdn.jsdelivr.net/npm/prismjs@1/plugins/line-numbers/prism-line-numbers.min.js"></script>
     </body>
 </html>