Add search engines to the default list

I'd like to add the following search engines to the default list:

• Startpage: https://www.startpage.com/
• Mojeek: https://www.mojeek.com/
• Brave Search: https://search.brave.com/
• Metager: https://metager.org/
• DuckDuckGo (HTML): https://html.duckduckgo.com/html/

If we can get this to the next alpha, it would be nice.

Is there anything you need me to prepare?