Development steps

1. Install required node js version (v10.15.3)

https://linuxconfig.org/how-to-install-nodejs-on-debian-9-stretch-linux

and use an older version:

https://stackoverflow.com/questions/7718313/how-to-change-to-an-older-version-of-node-js

2. Run "npm i" to setup some dependencies.

3. In theory, that should trigger two additional build commands, but those failed, so manually: npx gulp copy npx gulp sass