Update user interface section

### MDN URL

https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/user_interface

### What specific section or headline is this issue about?

Entire section but in particular the toolbar and addrerr bar buttons

### What information was incorrect, unhelpful, or incomplete?

Section was it written before Safari adopted web extensions, and prior to the implementation of Manifest V3. In particular, this means that the toolbar and address bar buttons would benefit from additional information.

### What did you expect to see?

Provide more up-to-date information on UI components.

### Do you have any supporting links, references, or citations?

_No response_

### Do you have anything more you want to share?

_No response_