Add slack url to global config
diff --git a/custom-theme/community.html b/custom-theme/community.html
index a0a6106..15820a0 100644
--- a/custom-theme/community.html
+++ b/custom-theme/community.html
@@ -19,7 +19,7 @@
                     <p text-center><a href="mailto:dev-unsubscribe@mynewt.apache.org">Unsubscribe</a></p>
                   <p> <a href="http://mail-archives.apache.org/mod_mbox/mynewt-dev/">Mail archives</a> </p>
                   <p> Find us on Slack:</p>
-                  <p> <a href="https://join.slack.com/t/mynewt/shared_invite/enQtNjA1MTg0NzgyNzg3LTZiYzgxNDQ3NmQ5ZWFkMTY4MjNjYTNmNGJjMDhiMmZiMWFjNDdkMzBlNzZjOWY0YzljYTBhYTg1YmRjYzljZDg"><img src="https://www.countit.com/images/add_to_slack.png" alt="Slack Icon" title="Join our Slack Community" /></a></p>
+                  <p> <a href="{{ config.extra.slack_url }}"><img src="https://www.countit.com/images/add_to_slack.png" alt="Slack Icon" title="Join our Slack Community" /></a></p>
                 </div>
         </div>
         <div class="col-md-4 mailing-list">
diff --git a/custom-theme/footer.html b/custom-theme/footer.html
index e6f3ae4..d5c1ece 100644
--- a/custom-theme/footer.html
+++ b/custom-theme/footer.html
@@ -8,11 +8,13 @@
         <div class="logos">
             <img src="/img/asf_logo_wide_small.png" alt="Apache" title="Apache">
             <small class="footnote">
-            Apache Mynewt, Mynewt, Apache, the Apache feather logo, and the Apache Mynewt project logo are either registered trademarks or trademarks of the Apache Software Foundation in the United States and other countries.
+                Apache Mynewt, Mynewt, Apache, the Apache feather logo, and the Apache Mynewt
+                project logo are either registered trademarks or trademarks of the Apache
+                Software Foundation in the United States and other countries.
             </small>
-             <a href="https://join.slack.com/t/mynewt/shared_invite/enQtNjA1MTg0NzgyNzg3LTZiYzgxNDQ3NmQ5ZWFkMTY4MjNjYTNmNGJjMDhiMmZiMWFjNDdkMzBlNzZjOWY0YzljYTBhYTg1YmRjYzljZDg">
+            <a href="{{ config.extra.slack_url }}">
                 <img src="/img/add_to_slack.png" alt="Slack Icon" title="Join our Slack Community" />
-             </a>
+            </a>
         </div>
     </div>
 </footer>
diff --git a/mkdocs.yml b/mkdocs.yml
index b1440ad..94cc3e4 100644
--- a/mkdocs.yml
+++ b/mkdocs.yml
@@ -69,6 +69,8 @@
             location: "Hilton Portland Downtown, Portland, OR, USA"
             date: "12-14 March, 2018"
 
+    slack_url: "https://join.slack.com/t/mynewt/shared_invite/enQtNjA1MTg0NzgyNzg3LTZiYzgxNDQ3NmQ5ZWFkMTY4MjNjYTNmNGJjMDhiMmZiMWFjNDdkMzBlNzZjOWY0YzljYTBhYTg1YmRjYzljZDg"
+
 copyright: "Apache Mynewt is available under Apache License, version 2.0."
 
 google_analytics: ["UA-72162311-1", "auto"]