tromoSM/YT-Premium-Patch ? reverse-engineered prompt

Build me a small browser add on that makes YouTube feel like the premium version on desktop and mobile.

I want it to work in Firefox, with support for Safari too if possible, and also have a plain JavaScript file that can be injected into YouTube for other browsers. The main thing is that when I open YouTube, the patch activates automatically or with a simple tap, and the site looks and behaves like premium is enabled. Keep it lightweight and focused on YouTube only.

Please include a simple way to install or use it, plus clear fallback instructions for Safari since it may not stay active after refresh. If needed, look up current browser docs online so the extension works with modern YouTube pages. Make the code easy to maintain, and include a basic README that explains how to use it and what each version is for.