Merge pull request #3516 from michelleN/mailing-list

chore(README): add ref to helm mailing list

README.md

@@ -63,7 +63,9 @@ You can reach the Helm community and developers via the following channels:
   - #helm-users
   - #helm-dev
   - #charts
-- Mailing List: https://groups.google.com/forum/#!forum/kubernetes-sig-apps
+- Mailing Lists:
+  - [Helm Mailing List](https://lists.cncf.io/g/cncf-kubernetes-helm)
+  - [Kubernetes SIG Apps Mailing List](https://groups.google.com/forum/#!forum/kubernetes-sig-apps)
 - Developer Call: Thursdays at 9:30-10:00 Pacific. [https://zoom.us/j/4526666954](https://zoom.us/j/4526666954)
 
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