Add Quad9 dns configuration

[aalmenar]

This add another DNS service to the default list.

If you want i can make a pull request with the most used ones like, opendns and so on. Also to include cloudflare for families and other from quad9, so the user can select most of them and save him from entering a lot of information by hand.

[kkebo]

Thank you for your pull request.

Which DNS services do you think should be added to the default list and why? If the default list become long, I think I need to improve the sidebar UI and add test code for each DNS service's validation.

[aalmenar]

Which DNS services do you think should be added to the default list and why? If the default list become long, I think I need to improve the sidebar UI and add test code for each DNS service's validation.

I would add quad9, opendns and some people may want to use NextDNS. Those are the ones I may like to include. But as you said maybe the ui needs some reworking if the list becomes large.

[kkebo]

OK, thanks.

I plan to add something like "Create from Template" here, and add Quad9, OpenDNS, NextDNS, CloudFlare, and Google Public DNS to it. Then, I'll remove all the current default list.

How about that?

I'll merge this pull request in the meantime after testing servers.