Make ‘Add a new service’ a button

This, along with putting it in a sticky footer, makes it consistent with
the ‘Add template’ and ‘Invite team member’ buttons.

app/templates/views/choose-account.html

@@ -36,7 +36,9 @@
       {% endif %}
     </ul>
   {% if can_add_service %}
-    <a href="{{ url_for('.add_service') }}" class="browse-list-link">Add a new service…</a>
+    <div class="js-stick-at-bottom-when-scrolling">
+      <a href="{{ url_for('.add_service') }}" class="button-secondary">Add a new service</a>
+    </div>
   {% endif %}
 
 {% endblock %}