feat(math): add optional MathJax support (#707)

* feat: add MathJax option

* docs: move math engine note

* refactor: update LaTeX documentation and improve MathJax integration

- Adjusted LaTeX documentation for clarity and formatting.
- Enhanced MathJax configuration in the templates to support both KaTeX and MathJax rendering.
- Removed deprecated comments and streamlined the script loading process for MathJax.
- Updated the passthrough extension settings in the Hugo configuration for better compatibility with LaTeX math expressions.

* docs: simplify LaTeX documentation and clarify configuration steps

- Updated LaTeX documentation to reflect that KaTeX is enabled by default, removing the need for manual activation.
- Added examples for using LaTeX math expressions and clarified the configuration for the passthrough extension in Hugo.
- Enhanced MathJax section to emphasize its use as an alternative rendering engine.

layouts/_partials/head.html

@@ -85,7 +85,8 @@
 
   <!-- KaTeX-->
   {{ $noop := .WordCount -}}
-  {{ if .Page.Store.Get "hasMath" -}}
+  {{- $engine := site.Params.math.engine | default "katex" -}}
+  {{ if and (.Page.Store.Get "hasMath") (eq $engine "katex") -}}
     <!-- TODO: make url configurable -->
     {{ $katexBaseUrl := "https://cdn.jsdelivr.net/npm/katex@latest/dist" }}
     {{ $katexCssUrl := printf "%s/katex%s.css" $katexBaseUrl (cond hugo.IsProduction ".min" "") -}}
@@ -103,6 +104,8 @@
         {{ end -}}
       {{ end -}}
     {{ end -}}
+  {{ else if and (.Page.Store.Get "hasMath") (eq $engine "mathjax") -}}
+    {{ partialCached "scripts/mathjax.html" . -}}
   {{ end -}}
 
   {{ partial "custom/head-end.html" . -}}

layouts/_partials/scripts/mathjax.html

@@ -0,0 +1,21 @@
+{{/* MathJax */}}
+{{ $mathjaxVersion := site.Params.math.mathjaxVersion | default "3" -}}
+{{ $mathjaxJsUrl := printf "https://cdn.jsdelivr.net/npm/mathjax@%s/es5/tex-chtml.js" $mathjaxVersion -}}
+<script defer id="MathJax-script" src="{{ $mathjaxJsUrl }}" crossorigin="anonymous" async></script>
+<script>
+  MathJax = {
+    loader: {
+      load: ["ui/safe"],
+    },
+    tex: {
+      displayMath: [
+        ["\\[", "\\]"],
+        ["$$", "$$"],
+      ],
+      inlineMath: [
+        ["\\(", "\\)"],
+        ["$", "$"],
+      ],
+    },
+  };
+</script>

layouts/_partials/tags.html

@@ -1,7 +1,7 @@
 <p class="hx:opacity-50 hx:text-sm hx:leading-7">
-{{- range $tag := .Params.tags -}}
-  {{- with $.Site.GetPage (printf "/tags/%s" $tag) -}}
-    <a class="hx:inline-block hx:mr-2" href="{{ .RelPermalink }}">#{{ .Title }}</a>
+  {{- range $tag := .Params.tags -}}
+    {{- with $.Site.GetPage (printf "/tags/%s" $tag) -}}
+      <a class="hx:inline-block hx:mr-2" href="{{ .RelPermalink }}">#{{ .Title }}</a>
+    {{- end -}}
   {{- end -}}
-{{- end -}}
-</p>
+</p>