add support for mermaid diagrams (#17213)

Signed-off-by: Nicolas De Loof <nicolas.deloof@gmail.com>

_includes/head.html

@@ -76,6 +76,8 @@
   {%- endif -%}
   {%- include analytics/feedback.html -%}
 
+  {% include mermaid.html %}
+
   {%- comment -%}
   preload fonts: https://www.freecodecamp.org/news/web-fonts-in-2018-f191a48367e8/
   we only preload the "woff2" variants, as older formats (woff, eot) are only used

_includes/mermaid.html

@@ -0,0 +1,7 @@
+<script type="module">
+    import mermaid from 'https://cdn.jsdelivr.net/npm/mermaid@10/dist/mermaid.esm.min.mjs';
+    mermaid.initialize({ startOnLoad: false });
+    await mermaid.run({
+        querySelector: '.language-mermaid',
+    });
+</script>