[enh] displaying language_code in preferences

searx/templates/preferences.html

         <select name='language'>
             <option value="all" {% if current_language == 'all' %}selected="selected"{% endif %}>{{ _('Automatic') }}</option>
             {% for lang_id,lang_name,country_name in language_codes %}
-            <option value={{ lang_id }} {% if lang_id == current_language %}selected="selected"{% endif %}>{{ lang_name}} ({{ country_name }})</option>
+            <option value={{ lang_id }} {% if lang_id == current_language %}selected="selected"{% endif %}>{{ lang_name}} ({{ country_name }}) - {{ lang_id }}</option>
             {% endfor %}
         </select>
         </p>