Added note to readme

Author: JuanM04

packages/adapter-vercel/README.md

@@ -31,6 +31,11 @@ export default {
       // if true, will split your app into multiple functions
       // instead of creating a single one for the entire app
       split: false
+
+			// which version of Node.js you want your serverless
+			// function to run on - it only works with edge=false
+			// and ENABLE_VC_BUILD=1
+      nodeVersion: '16.x'
     })
   }
 };