Add markdown utils

- External links open in a new tab
- Clicking on image open an image modal

templates/contest/list.html

@@ -32,7 +32,6 @@
 {% endblock %}
 
 {% block three_col_js %}
-  <script src="{{ static('libs/featherlight/featherlight.min.js') }}" type="text/javascript"></script>
   <script type="text/javascript">
     function changeTabParameter(newTab) {
       const url = new URL(window.location);

templates/contest/ranking-css.html

@@ -42,7 +42,6 @@
   }
 
   .featherlight-content {
-    border-radius: 10px;
     height: 80%;
     width:  60%;
     overflow: auto;