add an include for __common__/aboutext.html to extend about.html

searx/templates/__common__/about.html

@@ -60,3 +60,4 @@ Searx can be added to your browser's search bar; moreover, it can be set as the
 <p><a href="{{ url_for('stats') }}">Stats page</a> contains some useful data about the engines used.</p>
 
 </div>
+{% include "__common__/aboutextend.html" ignore missing %}