feat: add mermaid for rendering mermaid diagram codes (#92)

This PR adds mermaid support
It also only loads the mermaid js module only if a code block that uses mermaid is present on that page

layouts/_default/baseof.html

@@ -46,6 +46,12 @@
 <script defer src="{{ $c_js.Permalink }}" {{ printf "integrity=%q" $c_js.Data.Integrity | safeHTMLAttr }} crossorigin="anonymous"></script>
 {{- end }}
 {{- partial "mathjax.html" . -}}
+{{ if .Page.Store.Get "hasMermaid" }}
+    <script defer type="module">
+      import mermaid from 'https://cdn.jsdelivr.net/npm/mermaid/dist/mermaid.esm.min.mjs';
+      mermaid.initialize({ startOnLoad: true,theme: 'dark' });
+    </script>
+{{ end }}
 {{- if templates.Exists "partials/extra-foot.html" -}}{{- partial "extra-foot.html" . -}}{{- end }}
 </body>
 

layouts/_default/markup/render-codeblock-mermaid.html

@@ -0,0 +1,4 @@
+<pre class="mermaid">
+  {{- .Inner | safeHTML }}
+</pre>
+{{ .Page.Store.Set "hasMermaid" true }}