docs(contributing): list Node.js 20+ for sim-setup

Author: waleedlatif1

.github/CONTRIBUTING.md

@@ -152,6 +152,7 @@ It creates a `sim/` deployment directory, provisions the database, generates sec
 
 #### Requirements
 
+- Node.js 20 or newer
 - Docker must be installed and running on your machine
 
 ### Option 2: Using Docker Compose