build: Add npm for dev-ui

Bug-SiliconLabs: UIC-2987
Relate-to: https://github.com/Z-Wave-Alliance/z-wave-stack/wiki/ZPC
Origin: SiliconLabs#48
Signed-off-by: Philippe Coval <philippe.coval@silabs.com>

Author: rzr

helper.mk

@@ -25,6 +25,7 @@ packages+=nlohmann-json3-dev
 # TODO: remove for offline build
 packages+=curl wget python3-pip
 packages+=time
+packages+=yarnpkg
 
 rust_url?=https://sh.rustup.rs
 RUST_VERSION?=1.65.0