fix(mathjax): correct regex to match LaTeX expressions

Updated the regular expression pattern to accurately match
LaTeX expressions delimited by $$ instead of single $ symbols.
This resolves incorrect parsing of MathJax content wrapped with
double dollar signs, improving the rendering accuracy in HTML.

functions.php

@@ -930,7 +930,7 @@ function convertMathJaxInHTML($html)
     }
 
     // Use a regular expression to find LaTeX expressions within the HTML
-    $pattern = '/\$(.*?)\$/';
+    $pattern = '/\$\$(.*?)\$\$/';
     $callback = function ($matches) {
         $latex = $matches[1];
         try {