Rolls back to the old version of Matjax...

...and adds auto-transfer of formulas on mobile devices.

docs/_includes/head_custom.html

@@ -4,22 +4,17 @@
 {% elsif site.latex == "mathjax" %}
 
 <!-- Use MathJax to Render LaTeX in MarkDown -->
-<script>
-  MathJax = {
-    tex: {
-      inlineMath: [
-        ["$", "$"],
-        ["\\(", "\\)"],
-      ],
-      processEscapes: true,
-    },
-  };
+<script type="text/x-mathjax-config">
+  MathJax.Hub.Config({
+    tex2jax: {inlineMath: [['$','$']]},
+    "HTML-CSS": { linebreaks: { automatic: true } },
+    CommonHTML: { linebreaks: { automatic: true } },
+    SVG: { linebreaks: { automatic: true } }
+  });
 </script>
 <script
   type="text/javascript"
-  id="MathJax-script"
-  async
-  src="https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-mml-chtml.js"
+  src="https://cdn.jsdelivr.net/npm/mathjax@2/MathJax.js?config=TeX-AMS_HTML"
 ></script>
 
 {% elsif site.latex == "katex" %}