README: Add information about BlueOS

Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>

Author: patrickelectric

README.md

@@ -1,9 +1,11 @@
-# Overview
+> ⚠️ **Warning** ⚠️ The Companion onboard computer software is no longer being developed or supported. New projects and vehicles are recommended to use [BlueOS](https://blueos.cloud/docs/blueos/latest/) instead.
 
-> **Note** The information in this guide applies to ArduSub V3.5 and up. If you are running an older version, you should [update](/quick-start/installing-ardusub.md).
+# Overview
 
 ## ArduSub and the ArduPilot Project
 
+> **Note** The information in this guide applies to ArduSub V3.5 and up. If you are running an older version, you should [update](/quick-start/installing-ardusub.md).
+
 The ArduSub project is a fully-featured open-source solution for remotely operated underwater vehicles (ROVs) and autonomous underwater vehicles (AUVs). ArduSub is a part of the [ArduPilot project](http://ardupilot.org/), and was originally derived from the ArduCopter code. ArduSub has extensive capabilities out of the box including feedback stability control, depth and heading hold, and autonomous navigation.
 
 ArduSub is designed to be safe, feature-rich, open-ended, and easy to use even for novice users.