Add autorefresh_list experiment

This experiment/feature checks at regular intervals whether there are
updates to thread lists, and notifies the user via a snackbar when
an update exists.

Bug: #42
Change-Id: I98e4aa03a7080c6bff781ce7c850477433090957
diff --git a/src/options/experiments.html b/src/options/experiments.html
index e25254b..d132305 100644
--- a/src/options/experiments.html
+++ b/src/options/experiments.html
@@ -13,6 +13,7 @@
       <p data-i18n="experiments_description"></p>
       <form>
         <div class="option"><input type="checkbox" id="threadlistavatars"> <label for="threadlistavatars" data-i18n="threadlistavatars"></label></div>
+        <div class="option"><input type="checkbox" id="autorefreshlist"> <label for="autorefreshlist" data-i18n="autorefreshlist"></label></div>
         <div class="actions"><button id="save" data-i18n="save"></button></div>
       </form>
       <div id="save-indicator"></div>