fix: Correct issue with icon path

Author: roda82

overrides/partial/header.html

@@ -58,7 +58,7 @@
       </div>
     {% endif %}
     <button id="export-button" class="md-header__button md-icon" title="Export Citation">
-      {% set icon = mdi:format-quote-close %}
+      {% set icon = format-quote-close %}
       {% include ".icons/" ~ icon ~ ".svg" %}
   </button>
   <dialog id="citation-dialog">