Add Brave Search to available search engines

BraveSearch: https://search.brave.com/
BraveSearchOnion: https://search.brave4u7jddbv7cyviptqjc7jusxh72uik7zt6adtckl5f4nwy2v72qd.onion/

Info: https://brave.com/search/
Usage numbers (March 2022): https://nitter.net/brave/status/1499590357339627522 (10M queries per day)
Original announcement (June 2021): https://brave.com/brave-search-beta/