add mermaidjs to the index page

templates/index.html

@@ -149,4 +149,14 @@
   items.forEach(item => observer.observe(item));
 </script>
 
+<script type="module">
+  import mermaid from 'https://cdn.jsdelivr.net/npm/mermaid@9/dist/mermaid.esm.min.mjs';
+  mermaid.initialize({ startOnLoad: true });
+</script>
+
+<script nomodule src="https://unpkg.com/browse/mermaid@9.3.0/dist/mermaid.min.js"></script>
+<script nomodule>
+  mermaid.initialize({ startOnLoad: true });
+</script>
+
 </html>