How to listen to webpage button triggered copy events?

I want to create a simple chrome extension that replaces the url that you copied from the “share > Copy link” button of reddit with a short link, but I don’t know how to listen to the event of that specific button click or the copy to clipboard event triggered by the button click.

I tried using

document.addEventListener('copy', onCopy, true);

to trigger onCopy whenever something is copied to clipboard, but it seems to only trigger on copy events from context menu, not those from webpage elements.

I’m a beginner in javascript and chrome extension so every advice is appreciated.