Note NodeJS 18 is not supported (Koenkk#1641)

* Note NodeJS 18 is not supported

* Update README.md

Co-authored-by: Koen Kanters <[email protected]>

Author: deviantintegral

README.md

@@ -48,6 +48,8 @@ Docgen includes some scripts to help testing the page.
 
 ## VuePress
 
+Use Node.js 16 for building VuePress (other versions like Node.js 18 are not supported)
+
 ```bash
 # Install dependencies
 npm ci