Note that zulip-action is not being carried forward

Author: SeanTAllen

README.md

@@ -4,7 +4,10 @@ A GitHub Action for sending messages to Zulip, written in [Pony](https://www.pon
 
 ## Status
 
-zulip-action is in early development and has not yet been released.
+**This project is not being carried forward.** The idea was promising, but the
+approach didn't work out, so development has stopped and the repository is being
+archived. It was never released. The code and docs below are left in place for
+reference only.
 
 ## Usage