docs(README.md): add notice of final release and maintenance mode

README.md

@@ -1,3 +1,9 @@
+
+|![](https://upload.wikimedia.org/wikipedia/commons/thumb/1/17/Warning.svg/156px-Warning.svg.png) | Deis Workflow will soon no longer be maintained.<br />Please [read the announcement](https://deis.com/blog/2017/deis-workflow-final-release/) for more detail. |
+|---:|---|
+| 09/07/2017 | Deis Workflow [v2.18][] final release before entering maintenance mode |
+| 03/01/2018 | End of Workflow maintenance: critical patches no longer merged |
+
 # Deis Chart Repository
 
 |![](https://upload.wikimedia.org/wikipedia/commons/thumb/1/17/Warning.svg/156px-Warning.svg.png) | Kubernetes Helm has replaced Helm Classic. The charts in this repository are now deprecated. Workflow v2.9.0 will be the last release installable with Helm Classic (helmc). |
@@ -11,3 +17,4 @@ This repository contains Helm Classic Charts for Deis Workflow and its component
 [issues]: https://github.com/deis/charts/issues
 [prs]: https://github.com/deis/charts/pulls
 [k8s-home]: http://kubernetes.io
+[v2.18]: https://github.com/deis/workflow/releases/tag/v2.18.0