add barebones theme switcher

app/templates/users/settings.html

@@ -15,6 +15,11 @@
     </div>
   </form>
   <form method='post'>
+    <label for='theme'>Theme (beta)</label>
+    <select autocomplete='off' id='theme' name='theme'>
+      <option value='default' {{ 'selected' if get_prefers_theme() == 'style' }}>Default</option>
+      <option value='theme-otomotone' {{ 'selected' if get_prefers_theme() == 'theme-otomotone' }}>Otomotone (beta)</option>
+    </select>
     <label for='topic_sort_by'>Sort threads by:</label>
     <select id='topic_sort_by' name='topic_sort_by'>
       <option value='activity' {{ 'selected' if session['sort_by'] == 'activity' else '' }}>Latest activity</option>