Allow setting banner on campaing

app/views/campaigns/_settings_modal.html.erb

@@ -112,6 +112,13 @@
           </fieldset>
         <% end %>
 
+        <fieldset>
+          <label>Default reason for peer-to-peer campaigns</label>
+          <p><small>Use it to suggest a good, pre-filled reason for campaigners</small></p>
+          <textarea class='u-marginTop--15' rows='4' name='campaign[default_reason_for_supporting]' value='<%= @campaign.default_reason_for_supporting %>'></textarea>
+        </fieldset>
+      </section>
+
 			<hr>
 
       <section class='layout--two'>