Add LaTeX/MathJax hack

[hacks] / content / mathjax / head.html

<script>
    MathJax = {
        tex: {
            inlineMath: [['$', '$']],
        },
    };
</script>
<script id="MathJax-script" async src="https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-chtml-full.js">
</script>