Add initial inline progress update

Doesn't work yet

bookwyrm/templates/snippets/progress_update.html

@@ -0,0 +1,5 @@
+<div class="progress-update is-small">
+    on page
+    <input class="is-small" type="text" size="3">
+    of
+</div> 

bookwyrm/templates/snippets/shelve_button.html

@@ -63,6 +63,10 @@
         </div>
         {% endwith %}
     </div>
+
+    {% if active_shelf.identifier == 'reading' %}
+    {% include 'snippets/progress_update.html' %}
+    {% endif %}
 </div>
 
 {% endif %}