Add `DNS over HTTPS` option to proxy servers

[kai3341]

I'm trying to integrate SmartProxy addon and i2p daemon. All works perfectly, but I have to use SOCKS5 only proxies to resolve names. When I use SOCKS4 + DoH, an error happens when DoH trying to resolve *.i2p domain.

I think it will be OK solution to add setting DNS-over-HTTPS behavior with variants ["Default", "Off", "On"].

Default should not change anything Off should enforce browser NOT to use DoH On should enforce browser to use DoH

Optionally when DNS-over-HTTPS behavior is On, DoH-resolver may be configured explicitly

[salarcode]

This is a limitation from Extensions Api provided by the browsers. Look for proxyDNS in https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/API/proxy/ProxyInfo

[kai3341]

@salarcode I found another way: https://support.mozilla.org/en-US/kb/firefox-dns-over-https#w_excluding-specific-domains

[salarcode]

The thing is that Extensions don't have access to those settings.

[kai3341]

Found another link: https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/API/dns/resolve

[salarcode]

dns.resolve() is just a API that is available for extensions. The browser will still resolve the DNS by its own.

[salarcode]

Waiting for the feature: https://bugzilla.mozilla.org/show_bug.cgi?id=1455425