changed all slack links to new invite link

-made easier for "newer participants".

Author: vaibhavdaren

index.html

@@ -122,7 +122,7 @@
                         <li><a href="about.html">Team</a></li>
                         <li><a href="#fh5co-started" id="donate-us">Donate Us</a></li>
                         <li><a href="http://wiki.codeuino.org/">Wiki</a></li>
-                        <li><a href="https://goo.gl/3pwWMR">Get Involved</a></li>
+                        <li><a href="https://join.slack.com/t/codeuino/shared_invite/enQtMzcxOTQwNzE4NzcxLWEyNzUxYjI0ZThiNWUyYWI5MzJlMTNmODMxN2NjMTcxODJkZmFhNTVkYmUyOTQ1YzgzNTlmMTVkYzVhMzdmNTQ">Get Involved</a></li>
                     </ul>
                 </div>
             </div>