add nodejs version

Author: HenryHengZJ

README.md

@@ -9,6 +9,8 @@ Drag & drop UI to build your customized LLM flow using [LangchainJS](https://git
 
 ## ⚡Quick Start
 
+Download and Install [NodeJS](https://nodejs.org/en/download) >= 18.15.0
+
 1. Install Flowise
     ```bash
     npm install -g flowise