Update default.html

Author: pavly-gerges

_layouts/default.html

@@ -38,4 +38,5 @@ <h2 id="project_tagline">{{ site.description | default: site.github.project_tagl
       </footer>
     </div>
   </body>
+<script type="text/javascript" id="MathJax-script" async src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/3.0.0/es5/latest?tex-mml-chtml.js"> </script>
 </html>