Update README.md with link to ARCOS Tools Portal

Author: kityansiu

README.md

@@ -51,6 +51,8 @@ To make RACK easy for all ARCOS performers to use, we deploy RACK as a software
 
 RACK is available as both a Linux container and a virtual machine, and is supported on Linux, Windows, and MacOS systems. To learn more and get detailed instructions on how to get started, see our [Installation Instructions](https://github.com/ge-high-assurance/RACK/wiki/Home#installation-instructions).
 
+RACK is also available on the [ARCOS Tool Portal](https://arcos-tools.org/).
+
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 Copyright (c) 2021-2024 General Electric Company, Galois, Inc.