add cooper button

index.html

@@ -446,6 +446,15 @@
             <a href=https://highlysuspect.agency title='highly suspect agency'>
               <img src=media/buttons/hsa.gif alt='highly suspect agency'>
             </a>
+
+          <li id=cooper>
+            <a href=https://ottr.uk title=otterspace>
+              <picture>
+                <source srcset=media/buttons/cooper_still.png
+                        media='(prefers-reduced-motion: reduce)'>
+                <img src=media/buttons/cooper.gif alt=otterspace>
+              </picture>
+            </a>
         </ul>
       </section>