Build a bundle without manifest.js or other dependencies

Hi everyone! I make a js widget, what depend from my site data (widget get data by api, but it doesnt matter in the context of question). It connected to site by script tag

<script src="/widget/widget.js" assync></script>

css file is appending in script. Widget is work correctly, but on my site only. I found out, what it depend from manifest.js file - without this dependency it is doesnt work. Now im buiding widget bundle like this:

mix
.sass('resources/sass/widget.scss', 'public/widget/widget.css')
.js('resources/js/widget.js', 'public/widget/widget.js');

Could everyone explain, how to correctly build a bundle by laravel mix without this and other extra-dependency? (or, maybe, i should use pure webpack in this case?) Thanks in advance!