feat: Add working chrome UI

[herrfugbaum]

🛠 This PR adds the missing functionality from #5 but is still a work in progress 🛠

ToDo:

• [ ] Add styles
• [ ] Fix form values (for example the width sends 3 instead of 3px)
• [ ] Remove injected HTML when the toggle switch gets set to deactivated
• [ ] Check if we can remove the background.js as it doesn't make much sense any longer
• [ ] Check if we want to keep the return this statement in debucsser.js, currently it is added for debugging purposes
• [ ] Add documentation
• [ ] Make the UI accessible
• [ ] Decide how the activation button should behave when the extension popup gets closed

And probably some other things 😃