Updated all test methods to use namespace.katex instead of namespace.mathjax in test_namespace_production_custom_settings(),
test_namespace_development_custom_settings(), and test_namespace_simulate_expired_subscription().
Renamed test_mathjax_enabled_and_disabled() to test_katex_enabled_and_disabled().
Updated test to check cleaner.katex property instead of cleaner.mathjax.
Removed assertions about MathJax script tags.
Renamed checkbox from mathjax-checkbox to katex-checkbox.
Updated label to "Enable KaTeX" with link to katex.org.
Changed description from "could introduce slowness" to "fast math rendering".
Updated previewAjax() and sendPreview() functions to use katex parameter instead of mathjax.
Replaced MathJax.Hub.Queue() call with KaTeXrenderMathInElement() for live preview rendering.
Replaced MathJax CDN with KaTeX CDN. Now loads KaTeX CSS, JS, and
auto-render extension from jsdelivr.
Added auto-render configuration with
$$ and $ delimiters.