Add support for KaTeX formule

Per https://www.docsy.dev/docs/adding-content/diagrams-and-formulae/#latex-support-with-katex
we can have formulae. Make it so, and document this in the style guide.

Author: Tim Bannister

content/en/docs/contribute/style/style-guide.md

@@ -3,6 +3,7 @@ title: Documentation Style Guide
 linktitle: Style guide
 content_type: concept
 weight: 40
+math: true
 ---
 
 <!-- overview -->
@@ -317,6 +318,18 @@ kind: Pod
 ...
 ```
 
+## Formulae and equations
+
+You can use the Docsy support for [diagrams and formulae](https://www.docsy.dev/docs/adding-content/diagrams-and-formulae/#latex-support-with-katex).
+
+For example: `\\(\frac{7}{9} \sqrt{K^8 s}\\)`, which renders as \\(\frac{7}{9} \sqrt{K^8 s}\\).
+
+Prefer inline formulae where reasonable, but you can use a `math` block if that's likely to help readers.
+
+Read the Docsy guide to find out what you need to change in your page to activate support;
+if you have problems, add `math: true` to the page [front matter](https://gohugo.io/content-management/front-matter/)
+(you can do this even if you think the automatic activation should be enough).
+
 ## Kubernetes.io word list
 
 A list of Kubernetes-specific terms and words to be used consistently across the site.

layouts/partials/scripts.html

@@ -10,6 +10,23 @@
 <script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/mermaid.min.js" integrity="sha512-IX+bU+wShHqfqaMHLMrtwi4nK6W/Z+QdZoL4kPNtRxI2wCLyHPMAdl3a43Fv1Foqv4AP+aiW6hg1dcrTt3xc+Q==" crossorigin="anonymous"></script>
 {{- end }}
 
+{{ $needKaTeX  := or .Site.Params.katex.enable .Params.math .Params.chem -}}
+{{ if  $needKaTeX -}}
+{{/* load stylesheet and scripts for KaTeX support */ -}}
+<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/[email protected]/dist/katex.min.css"
+      integrity="sha512-6VMVcy7XQNyarhVuiL50FzpgCFKsyTd6YO93aaQEyET+BNaWvj0IgKR86Bf6+AmWczxAcSnL+JGjo+iStgO1gQ==" crossorigin="anonymous">
+  {{/* The loading of KaTeX is deferred to speed up page rendering */ -}}
+<script defer src="https://cdn.jsdelivr.net/npm/[email protected]/dist/katex.min.js"
+        integrity="sha512-b9IKj4LCNrtCPBhceRcoYOHWW/S2q9fpl7iAJlyxYpykRj1SKM7FE9+E0NEnJ8g8ni47LBr2GuX9qzg/xeuwzQ=="
+        crossorigin="anonymous">
+</script>
+  {{/* To automatically render math in text elements, include the auto-render extension: */ -}}
+<script defer src="https://cdn.jsdelivr.net/npm/[email protected]/dist/contrib/auto-render.min.js"
+       integrity="sha512-iWiuBS5nt6r60fCz26Nd0Zqe0nbk1ZTIQbl3Kv7kYsX+yKMUFHzjaH2+AnM6vp2Xs+gNmaBAVWJjSmuPw76Efg==" crossorigin="anonymous"
+       {{ printf "onload='renderMathInElement(%s, %s);'" (( $.Page.Site.Params.katex.html_dom_element | default "document.body" ) | safeJS ) ( printf "%s" ( $.Page.Site.Params.katex.options | jsonify )) | safeHTMLAttr }}>
+</script>
+{{ end -}}
+
 {{ $jsBs := resources.Get "vendor/bootstrap/dist/js/bootstrap.bundle.js" -}}
 {{ $jsBase := resources.Get "js/base.js" }}
 {{ $jsAnchor := resources.Get "js/anchor.js" }}