Update README.md with mailing list details (#671)

[chore] Update readme with mailing list details

Author: starryeyez024

README.md

@@ -34,6 +34,11 @@ _Note: You will need to use [Node](https://nodejs.org/en/) v.7 or higher._
 Though we have tested and verified general usability within these frameworks, PFE makes no guarantees about compatibility within specific sites & applications. Please test accordingly. For more details, check out the [official status card per component](https://github.com/patternfly/patternfly-elements/issues?q=is%3Aopen+is%3Aissue+label%3A%22status+tracking+only%22) or visit the [status page on the documentation site](https://patternfly.github.io/patternfly-elements/getting-started/component-status/). 
 
 
+## Stay informed
+
+Sign up for the for the [active project participation email list](https://www.redhat.com/mailman/listinfo/patternfly-elements-contribute) and/or the [informed email list](https://www.redhat.com/mailman/listinfo/patternfly-elements-announce).
+
+You can also participate in discussions on [patternfly.slack.com](https://patternfly.slack.com) in the #patternfly-elements channel.
 
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