Revert "Revert "Update MathJax to v3""; MathJax 3.0.1 released

This reverts commit 6b16f61.

Ref:
#12 (comment)

layouts/partials/mathjax.html

@@ -6,6 +6,6 @@
      that 'unsafe-inline can also be removed from script-src CSP.
 -->
 <script src="{{ "js/mathjax-config.js" | absURL }}"></script>
- <!-- https://gohugo.io/content-management/formats/#mathjax-with-hugo -->
-<script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.4/MathJax.js?config=TeX-AMS_HTML"></script>
-<!-- <script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.4/MathJax.js?config=TeX-MML-AM_CHTML"></script> -->
+
+<!-- Use MathJax 3 for faster loading -->
+<script type="text/javascript" src="https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-chtml.js"></script>

static/js/mathjax-config.js

@@ -1,17 +1,5 @@
 window.MathJax = {
-    displayAlign: "center",
-    displayIndent: "0em",
-    "HTML-CSS": { scale: 100,
-                  linebreaks: { automatic: "false" },
-                  webFont: "TeX"
-                },
-    SVG: {scale: 100,
-          linebreaks: { automatic: "false" },
-          font: "TeX"},
-    NativeMML: {scale: 100},
-    TeX: { equationNumbers: {autoNumber: "AMS"},
-           MultLineWidth: "85%",
-           TagSide: "right",
-           TagIndent: ".8em"
-         }
+  tex: {
+    tags: "ams"
+  }
 };