Replace polyfill.io with Cloudflare Image

Signed-off-by: Lei Hsiung <leihsiung.ray@gmail.com>

index.html

@@ -57,7 +57,7 @@ Exploring Refusal Loss Landscapes </title>
 
 
 <!-- for mathjax support -->
-    <script src="https://polyfill.io/v3/polyfill.min.js?features=es6"></script>
+    <script src="https://cdnjs.cloudflare.com/polyfill/v3/polyfill.min.js?features=es6"></script>
     <script id="MathJax-script" async src="https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-mml-chtml.js"></script>