README: Add disclaimer that this code is no longer being developed

Signed-off-by: Matthias J. Kannwischer <matthias@kannwischer.eu>

Author: mkannwischer

README.md

@@ -1,5 +1,8 @@
 [//]: # (SPDX-License-Identifier: CC-BY-4.0)
 
+
+**MLKEM-C-EMBEDDED is no longer und active development and maintenance. You may want to consider [mlkem-native](https://github.com/pq-code-package/mlkem-native) instead.**
+
 **MLKEM-C-EMBEDDED** is a collection of [MLKEM](https://doi.org/10.6028/NIST.FIPS.203.ipd) implementations optimized for embedded microcontrollers.
 It is free software licensed under an Apache-2.0 license.
 
@@ -38,7 +41,6 @@ In the long term, possible extensions are
 
 **MLKEM-C-EMBEDDED** is currently a work in progress and we do not recommend relying on it at this point.
 **WE DO NOT CURRENTLY RECOMMEND RELYING ON THIS LIBRARY IN A PRODUCTION ENVIRONMENT OR TO PROTECT ANY SENSITIVE DATA.**
-Once we have the first stable version, this notice will be removed
 
 The current code is compatible with the [`standard` branch of the official MLKEM repository](https://github.com/pq-crystals/kyber/tree/standard).