add MathJax to test dashboard

Author: etpinard

devtools/test_dashboard/index.html

@@ -19,8 +19,8 @@
   </div>
   <div id="snapshot"></div>
 
+  <script type="text/javascript" src="../../dist/extras/mathjax/MathJax.js?config=TeX-AMS-MML_SVG"></script>
   <script id="source" type="text/javascript" src="../../build/plotly.js"></script>
   <script type="text/javascript" src="../../build/test_dashboard-bundle.js"></script>
 </body>
 </html>
-