adding a link to our Linkedin group

Author: angelobanse

content/contact.md

@@ -111,10 +111,11 @@ This is also the way to notify us if you find any typos or errors in our Documen
 Social media</h4><br>
 Occasional development updates are posted on our social media channels. Follow us and stay informed!
 <br><br>
-<a href="https://www.facebook.com/simulationofurbanmobility/"><button class="btn btn-sm btn-outline-info">Facebook</button></a>
-<a href="https://twitter.com/EclipseSumo"><button class="btn btn-sm btn-outline-info">X</button></a>
-<a href="https://instagram.com/eclipse.sumo"><button class="btn btn-sm btn-outline-info">Instagram</button></a>
-<a href="https://www.threads.net/@eclipse.sumo"><button class="btn btn-sm btn-outline-info">Threads</button></a>
+<a href="https://www.facebook.com/simulationofurbanmobility/"><button class="btn btn-sm btn-outline-info"><i class="fa-brands fa-facebook"></i></button></a>
+<a href="https://twitter.com/EclipseSumo"><button class="btn btn-sm btn-outline-info"><i class="fa-brands fa-x-twitter"></i></button></a>
+<a href="https://instagram.com/eclipse.sumo"><button class="btn btn-sm btn-outline-info"><i class="fa-brands fa-instagram"></i></button></a>
+<a href="https://www.threads.net/@eclipse.sumo"><button class="btn btn-sm btn-outline-info"><i class="fa-brands fa-threads"></i></button></a>
+<a href="https://www.linkedin.com/groups/5156801/"><button class="btn btn-sm btn-outline-info"><i class="fa-brands fa-linkedin"></i></button></a>
 </div>
 
 <!-- chat -->

themes/sumo-theme/layouts/index.html

@@ -138,7 +138,8 @@
         <a class="btn btn-light" href="https://twitter.com/eclipsesumo" aria-label="X"><span class="fab fa-x-twitter"></span></a>
         <a class="btn btn-light" href="https://facebook.com/simulationofurbanmobility" aria-label="Facebook"><span class="fab fa-facebook"></span></a>
         <a class="btn btn-light" href="https://instagram.com/eclipse.sumo" aria-label="Instagram"><span class="fab fa-instagram"></span></a>
-        <a class="btn btn-light" href="https://www.threads.net/@eclipse.sumo" aria-label="Instagram"><span class="fab fa-threads"></span></a>
+        <a class="btn btn-light" href="https://www.threads.net/@eclipse.sumo" aria-label="Threads"><span class="fab fa-threads"></span></a>
+        <a class="btn btn-light" href="https://www.linkedin.com/groups/5156801/" aria-label="Linkedin"><span class="fab fa-linkedin"></span></a>
         <a class="btn btn-light" href="https://chat.eclipse.org/#/room/#automotive.sumo:matrix.eclipse.org" aria-label="Matrix"><span class="fas fa-comments"></span></a>
         <a class="btn btn-light" href="{{ `contact` | absURL }}" aria-label="contact"><span class="fas fa-envelope"></span></a>
       </div>