add support in footer to linkedin url

Author: Eitan Behar

_includes/footer.html

@@ -10,6 +10,13 @@
     </a>
   </li>
 </ul>{% endif %}
+{% if site.linkedin %}<ul class="list-inline mb-0">  
+  <li class="list-inline-item mx-2 h3" data-toggle="tooltip" data-placement="top" title="" aria-label="Linkedin" data-original-title="Linkedin">
+    <a class="text-white" target="_blank" href="https://linkedin.com/in/{{ site.linkedin }}">
+      <i class="fab fa-linkedin"></i>
+    </a>
+  </li>
+</ul>{% endif %}
 </div>
 <div class="col-6 col-sm-4 text-right text-xs-center order-sm-3">
 <ul class="list-inline mb-0">