Update README.md

Author: chen-robert

README.md

@@ -3,7 +3,9 @@
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-rCTF is redpwnCTF's CTF platform. It is developed and (used to be) maintained by the [redpwn](https://redpwn.net) CTF team.
+**This version is no longer maintained, please submit issues and feature requests to [otter-sec/rctf](https://github.com/otter-sec/rctf).**
+
+rCTF is redpwnCTF's CTF platform. It is developed by the [redpwn](https://redpwn.net) CTF team.
 
 ## Getting Started