feat: enable KaTeX rendering with additional delimiters (#19)

* Support rendering math equations using $ or $$ as delimiters.

* Also, format the code by .pretterrc.

layouts/partials/helpers/katex.html

@@ -1,8 +1,28 @@
-<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/katex@0.16.4/dist/katex.min.css" integrity="sha384-vKruj+a13U8yHIkAyGgK1J3ArTLzrFGBbBc0tDp4ad/EyewESeXE/Iv67Aj8gKZ0" crossorigin="anonymous">
+<link
+  rel="stylesheet"
+  href="https://cdn.jsdelivr.net/npm/katex@0.16.4/dist/katex.min.css"
+  integrity="sha384-vKruj+a13U8yHIkAyGgK1J3ArTLzrFGBbBc0tDp4ad/EyewESeXE/Iv67Aj8gKZ0"
+  crossorigin="anonymous"
+/>
 
 <!-- The loading of KaTeX is deferred to speed up page rendering -->
-<script defer src="https://cdn.jsdelivr.net/npm/katex@0.16.4/dist/katex.min.js" integrity="sha384-PwRUT/YqbnEjkZO0zZxNqcxACrXe+j766U2amXcgMg5457rve2Y7I6ZJSm2A0mS4" crossorigin="anonymous"></script>
+<script
+  defer
+  src="https://cdn.jsdelivr.net/npm/katex@0.16.4/dist/katex.min.js"
+  integrity="sha384-PwRUT/YqbnEjkZO0zZxNqcxACrXe+j766U2amXcgMg5457rve2Y7I6ZJSm2A0mS4"
+  crossorigin="anonymous"
+></script>
 
 <!-- To automatically render math in text elements, include the auto-render extension: -->
-<script defer src="https://cdn.jsdelivr.net/npm/katex@0.16.4/dist/contrib/auto-render.min.js" integrity="sha384-+VBxd3r6XgURycqtZ117nYw44OOcIax56Z4dCRWbxyPt0Koah1uHoK0o4+/RRE05" crossorigin="anonymous"
-    onload="renderMathInElement(document.body);"></script>
+<script
+  defer
+  src="https://cdn.jsdelivr.net/npm/katex@0.16.4/dist/contrib/auto-render.min.js"
+  integrity="sha384-+VBxd3r6XgURycqtZ117nYw44OOcIax56Z4dCRWbxyPt0Koah1uHoK0o4+/RRE05"
+  crossorigin="anonymous"
+  onload="renderMathInElement(document.body, {
+      delimiters: [
+        {left: '$$', right: '$$', display: true},
+        {left: '$', right: '$', display: false}
+      ]
+    });"
+></script>