Clone this repo into extensions/cupnoodles/noodleutils and then run a composer install.
php artisan noodle:watch is a assets/src/ directory watcher that runs igniter:util CompileJS and igniter:util CompileSCSS on any change to the assets/src/ folder.
Please note that it assumes a standard directory structure on your main theme and isn't pulling asset bundle paths from your assets.json. Update the code in Watch.php if you're using non-standard asset paths.
Also note! Unlinke running igniter:util CompileSCSS, noodle:watch will compile theme variables into your CSS. This can lead to you having undefined variables in your SCSS that are only set through the them editor, causing such themes to fail to compile unless you're diligent about setting default values.