How to set up Opus Media Recorder properly?

Question

I am trying to get opus media recorder to work but I seem to fail to understand the installation process/concept.

This is the JS-Code that I use to set it up (following the fiddle example on the project's github page: https://github.com/kbumsik/opus-media-recorder):

<script src="https://cdn.jsdelivr.net/npm/opus-media-recorder@latest/OpusMediaRecorder.umd.js"></script>
<script src="https://cdn.jsdelivr.net/npm/opus-media-recorder@latest/encoderWorker.umd.js"></script>
<script>

const workerOptions = {
  OggOpusEncoderWasmPath: 'https://cdn.jsdelivr.net/npm/opus-media-recorder@latest/OggOpusEncoder.wasm',
  WebMOpusEncoderWasmPath: 'https://cdn.jsdelivr.net/npm/opus-media-recorder@latest/WebMOpusEncoder.wasm'
};

// Replace MediaRecorder
window.MediaRecorder = OpusMediaRecorder;

But when I later want to set up the recorder (after getUserMedia), the following error appears:

Uncaught (in promise) TypeError: Failed to execute 'fetch' on 'WorkerGlobalScope': Failed to parse URL from /WebMOpusEncoder.wasm

My question: Do I need to install anything server-side for this to work? Or does opus media recorder solely rely on js magic and if so:

What am I missing to properly set it up?