How to use RxJS from Chrome Extensions service worker?

Question

I am able to successfully use RxJs 7.8.0 from my Chrome Extension's popup.js and options.js by importing RxJS from their corresponding popup.html and options.html files like this:

<script type="text/javascript" src="./libs/rxjs.umd.js"></script>
<script type="module" src="options.js"></script>

However, I also have background.js from which I would like to use RxJs. This is service worker and does not have html file. So when I try to import RxJs like this:

import * as rxjs from "./libs/rxjs.umd.js";

My chrome extension gets following error:

Uncaught TypeError: Cannot set properties of undefined (setting 'rxjs')
libs/rxjs.umd.js:416 (anonymous function)

Which corresponds to following code:

413:(function (global, factory) {
414:    typeof exports === 'object' && typeof module !== 'undefined' ? factory(exports) :
415:    typeof define === 'function' && define.amd ? define('rxjs', ['exports'], factory) :
416:    (factory((global.rxjs = {})));
417:}(this, (function (exports) { 'use strict';

I am able to successfully import other libraries from my background.js file. So this seems to be something specific to RxJs. If it matters I got RxJs from this CDN