Update README.md

Author: cbanner

samples/music-festival-vue-decoupled/README.md

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+> [!WARNING]
+> This example is intended for demonstration purposes only and is not supported for production applications in Optimizely's Content and Commerce Cloud. The approach launches a NodeJS server and proxies requests to a frontend application, which can result in performance and stability issues.
+
 # Optimizely Content Delivery - Decoupled
 
 This sample site demonstrates one approach to render Optimizely content in a client side framework that is using client side routing for navigation with a working On-Page Edit (OPE) mode in the Optimizely UI, where the frontend and backend are hosted as separate apps.