Adding support for mermaid and mathJax

partials/after_footer.ejs

@@ -1,6 +1,7 @@
 <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
 <script src="https://cdnjs.cloudflare.com/ajax/libs/clipboard.js/2.0.0/clipboard.min.js"></script>
 <script src="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/9.13.1/highlight.min.js"></script>
+<script src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.5/MathJax.js?config=TeX-MML-AM_CHTML"></script>
 <%- js("js/vendor.min") %>
 
 <% if (theme.graphviz.enable) { %>
@@ -34,3 +35,12 @@
     });
   });
 </script>
+
+<% if (theme.mermaid.enable) { %>
+  <script src='https://unpkg.com/mermaid@<%= theme.mermaid.version %>/dist/mermaid.min.js'></script>
+  <script>
+    if (window.mermaid) {
+      mermaid.initialize({theme: 'forest'});
+    }
+  </script>
+<% } %>