the Mnk ,
( Tom , how to tag names with spaces eg The Mnk above ?)
I am not affiliated with them in any way but....
Enigma Virtual Box (free, ive used and works well) will allow you to turn your nwjs package into a fairly secure exe
and Enigma Protector ($199, ive not tried) will allow you to hardlock the exe to a unique machine / user with unique licence serial number access keys distributed by yourself.
both products can be found here.
as TheRealDannyyy says though its likely all cracked allready if you go search the right places.
But it would at least deter casual / lazy sharing of assets and game.
also Im not sure if dev tools is accessible through nwjs apps, possibly not, but if it is it would make all this pointless.
also if you are putting your game on steam I am pretty sure they have some DRM options.