How to create a video-linked browser extension?

Question

Browser extensions

Hello. I ask for help in writing an extension for Chrome and Firefox browsers.
The idea is that the extension switches the video (let's say on YouTube) to the next one after a certain period of viewing. Ideally, bind this extension to a specific browser tab (not the page address) and set the viewing time interval itself, with the ability to change these settings. It is planned to share this extension with third parties.
I'm a total novice on this subject, so please don't criticize too much.

Answer 1

Read
https://developers.google.com/youtube/iframe_api_r...
https://developer.mozilla.org/ru/docs/Mozilla/Add-...