Consider standardizing 7-day max-age cap for cookies set via JavaScript

Two browsers are already doing this ([Safari](https://webkit.org/blog/8613/intelligent-tracking-prevention-2-1/) and [Brave](https://brave.com/privacy-features/#:~:text=Brave%20caps%20the%20life%20of,clear%20cookies%20at%20any%20time.)). It might be worth documenting in the standard.