make Slack link more obvious

Author: pcarruscag

_includes/topnav.html

@@ -18,13 +18,13 @@
                 <li {% if page.sectionid=='docs' %} class="active" {% endif %}><a href="{{ "/docs_v7/home/" | relative_url }}">Docs</a></li>
                 <li {% if page.sectionid=='tutorials' %} class="active" {% endif %}><a href="{{ "/tutorials/home/" | relative_url }}">Tutorials</a></li>
                 <li {% if page.sectionid=='vandv' %} class="active" {% endif %}><a href="{{ "/vandv/home/" | relative_url }}">V&V</a></li>
-                <li {% if page.sectionid=='forum' %} class="active" {% endif %}><a href="{{ "https://www.cfd-online.com/Forums/su2/" }}">Forum</a></li>
+                <li {% if page.sectionid=='forum' %} class="active" {% endif %}><a href="{{ "https://www.cfd-online.com/Forums/su2/" }}">User Forum</a></li>
+                <li {% if page.sectionid=='slack' %} class="active" {% endif %}><a href="{{ "https://join.slack.com/t/su2devteam/shared_invite/zt-af0uuqf8-8XNExKMV9G~UVsnkvi5uVA" }}">Dev Team Slack</a></li>
                 <li {% if page.sectionid=='develop' %} class="active" {% endif %}><a href="{{ "/develop.html" relative_url }}">Develop</a></li>
             </ul>
             <div class="navbar-right">
                 <ul class="nav navbar-nav">
                     <li><a href="https://www.youtube.com/channel/UCxv_00gWLAQPBUnl9mGRQjA"><i class="fab fa-youtube" aria-hidden="true"></i></a></li>
-                    <li><a href="https://join.slack.com/t/su2devteam/shared_invite/zt-af0uuqf8-8XNExKMV9G~UVsnkvi5uVA"><i class="fab fa-slack-hash" aria-hidden="true"></i></a></li>
                     <li><a href="{{ site.git_address }}"><i class="fab fa-github" aria-hidden="true"></i></a></li>
                     <li><a href="https://twitter.com/intent/user?screen_name=su2code"><i class="fab fa-twitter" aria-hidden="true"></i></a></li>
                     <li><a href="https://www.facebook.com/su2code/"><i class="fab fa-facebook" aria-hidden="true"></i></a></li>