DNS-over-HTTPS (DoH) Implementation to Support Custom DNS Providers

[ritambaishya]

To enhance Vivaldi's DNS-over-HTTPS (DoH) capabilities, consider adding a "Custom DoH Server" option in the privacy settings. This would allow users to manually enter the full DoH endpoint URL (e.g., https://dns.nextdns.io/dns-query), enabling the use of advanced DNS services like NextDNS.
Additionally, an input field for API keys could be included for providers that require them. This increased flexibility would empower users to choose their preferred DNS provider, improving privacy, security, and overall user experience.

[DoctorG]

@ritambaishya At internal Vivaldi page chrome:settings/security a URL already can be set.