1.1.1.1 DNS over HTTPS support

[Peter200lx]

With the new https://1.1.1.1 CloudFlare DNS provider we have another public DNS over HTTPS server to use. Additionally they support the same JSON format as Google's DNS over HTTPS. It would be nice to add 1.1.1.1 as an alternative for providing secured DNS.
Here is is the developer/api page:
https://developers.cloudflare.com/1.1.1.1/dns-over-https/json-format/

[rpwoodbu]

I'm all for it! Should be pretty easy to add if the protocol is really the same, but even if it isn't, I made the code pretty modular. Pull requests are welcome.

[rpwoodbu]

Google Public DNS just announced RFC 8484 support. If 1.1.1.1 is compliant (unclear from a cursory examination of their website), then it would be good to convert to that and provide one unified solution.