Merge pull request #38 from StreetScienceCommunity/google-group

Fix link to google group in footer

Author: bebatut

_includes/default-footer.html

@@ -20,7 +20,7 @@ <h3>Get in touch</h3>
           <br />
           <i class="fas fa-envelope"></i>
           Join the 
-          <a href="{{ site.participation_form }}">mailing list</a>
+          <a href="{{ site.google_group }}">mailing list</a>
         </p>
       </div>
       <div class="column is-5">