feat(math): add optional MathJax support (#707)

* feat: add MathJax option

* docs: move math engine note

* refactor: update LaTeX documentation and improve MathJax integration

- Adjusted LaTeX documentation for clarity and formatting.
- Enhanced MathJax configuration in the templates to support both KaTeX and MathJax rendering.
- Removed deprecated comments and streamlined the script loading process for MathJax.
- Updated the passthrough extension settings in the Hugo configuration for better compatibility with LaTeX math expressions.

* docs: simplify LaTeX documentation and clarify configuration steps

- Updated LaTeX documentation to reflect that KaTeX is enabled by default, removing the need for manual activation.
- Added examples for using LaTeX math expressions and clarified the configuration for the passthrough extension in Hugo.
- Enhanced MathJax section to emphasize its use as an alternative rendering engine.

exampleSite/hugo.yaml

@@ -58,7 +58,7 @@ markup:
     extensions:
       passthrough:
         delimiters:
-          block: [['\[', '\]'], ["$$", "$$"]]
+          block: [['\[', '\]'], ['$$', '$$']]
           inline: [['\(', '\)']]
         enable: true