GitHub files/gists and npm uploads are embedded with Script tags
GitHub Gists can be embedded via Script Tags. So can any public GitHub file, actually.
Anyone can create an NPM account and upload packages. Those packages can be installed via npm, or got in a script tag via CDNs like jsdelivr.
…or you could just make a Google Apps Script with an endpoint that delivers a text file.
Examples
GitHub Gist
<script src="https://gist.github.com/aarongilly/58163e4387e6e4c6ccfb8e97062e59c2.js"></script>