Enhance accessibility of MathJax script loading with `cdnjs` (#1304)

* Add fallback mechanism for MathJax script loading to enhance global accessibility.

* Update mkdocs.yml

* Update mathjax.js

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Co-authored-by: Yudong Jin <krahets@163.com>

mkdocs.yml

@@ -143,7 +143,7 @@ markdown_extensions:
 extra_javascript:
   - javascripts/mathjax.js
   - https://polyfill.io/v3/polyfill.min.js?features=es6
-  - https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-mml-chtml.js
+  - https://cdnjs.cloudflare.com/ajax/libs/mathjax/3.2.2/es5/tex-mml-chtml.min.js
   # - javascripts/katex.js 
   # - https://cdnjs.cloudflare.com/ajax/libs/KaTeX/0.16.7/katex.min.js  
   # - https://cdnjs.cloudflare.com/ajax/libs/KaTeX/0.16.7/contrib/auto-render.min.js