Make certificate information accessible to JavaScript

[bsclifton]

Carried over from brave/browser-laptop#12904

Original post by @mikemaccana:

Hey there! There's a few reasons it could be advantageous to make certificate information available to JavaScript - either as part of the window or the Extensions API.

Description

This would allow developers to:

• Measure the cipher strength
• Display identify info
• Display contextual info about parent certs

To audiences ranging from from:

• infosec people (running headless browsers
• web developers (hey, this is BadCA, are you sure you want to trust it?)
• users ('This is 'Apple, Inc' in USA, this is apple.com-mg in Malaysia')

Right now the only people who can do anything requiring reading cert info is people who have the ability to ship Chromium based products.

There's a few places this has been raised over the years but Chromium are adding support for the TLS extension to the webrequest API.