Description

Please implement the "Enabling Sites to Determine Brave" Spec

Search for "Enabling Sites to Determine Brave" in G-Drive for the Spec
(also described in below post)
cc @snyderp

Android Link: #8215
iOS Link: brave/brave-ios#2323

Test plan

1. Visit https://jsbin.com/sexawix/edit?html,js,console
2. Output from console should look like:

"Brave detected"