import externalutil from 'https://externalutil.com/js/externalutil.js';
Module not found: 'https://externalutil.com/js/externalutil.js'
import URL's (as of yet). You should download the file, put it somewhere locally and reference it locally as well.
However in your case, I'd just use a
<script /> tag to include it in your html and just access the
window object. Converting it would be more hassle than it would be beneficial.