Put spanish back

Author: bethac07

_config.yml

@@ -42,7 +42,7 @@ html:
     hypothesis: true
   extra_footer: |
     <p>
-    <a href="https://www.bioimagingguide.org">English</a> <a href="https://cs.bioimagingguide.org">česky</a> <a href="https://pt.bioimagingguide.org">português</a>  <a href="https://ja.bioimagingguide.org">日本語</a> 
+    <a href="https://www.bioimagingguide.org">English</a> <a href="https://cs.bioimagingguide.org">česky</a> <a href="https://pt.bioimagingguide.org">português</a> <a href="https://es.bioimagingguide.org">español</a> <a href="https://ja.bioimagingguide.org">日本語</a> 
     </p>
 
 sphinx: