adding mermaidjs shortcode with example

layouts/partials/head.html

@@ -48,6 +48,11 @@
 <script src="{{ "js/bootstrap-4.3.1.min.js" | relURL }}"></script>
 <script src="{{ "js/sweetalert-2.1.2.min.js" | relURL }}"></script>
 
+{{ if eq .Params.mermaid true }}
+<!-- Copied from https://unpkg.com/mermaid@8.5.0/dist/mermaid.min.js -->
+<script async src="{{ "js/mermaid.min.js" | relURL }}"></script>
+{{ end }}
+
 <script src="{{ "js/script.js" | relURL }}"></script>
 <script src="{{ "js/custom-jekyll/tags.js" | relURL }}"></script>
 {{ with .Params.js }}{{ range (split . ",") }}<script src="{{ (trim . " ") | relURL }}"></script><!-- custom js added -->

layouts/shortcodes/mermaid.html

@@ -0,0 +1,10 @@
+<div class="mermaid">
+    {{.Inner}}
+</div>
+<!-- Hide content and error if JS is disabled. -->
+<noscript>
+    <style type="text/css">
+    .mermaid { display:none; }
+    </style>
+    <h4>[JavaScript must be <a href="https://www.enable-javascript.com/">enabled</a> to view content]</h4>
+</noscript>