Revamp the known DNS providers doc

[ameshkov]

1. Change how ToC is generated:

   toc_min_heading_level: 2
   toc_max_heading_level: 4

2. There are many small personal resovlers which are not in their specific section.

3. Add "## Public Anycast Resolvers" section for big resolvers with nice IP addresses that run anycast network.

4. Add "## Regional Resolvers" section for smaller resolvers that are hosted in 1-2 regions and not worldwide.

## Public Anycast Resolvers
These are large-scale DNS resolvers that are distributed around the world. They use anycast routing to direct your DNS queries to the nearest data center.

• AdGuard DNS
• CleanBrowsing
• Comodo Secure DNS
• Neustar Recursive DNS
• Cisco OpenDNS
• Google DNS
• Cloudflare DNS
• Quad9 DNS
• Verisign Public DNS
• Dyn DNS
• Safe DNS
• Ali DNS
• CFIEC Public DNS
• Nawala Childprotection DNS
• 360 Secure DNS
• DNSPod Public DNS+
• Freenom World
• Strongarm DNS -- rename to DNSWatchGO, link https://www.watchguard.com/wgrd-products/dnswatchgo
• SafeSurfer DNS
• DeCloudUs DNS
• DNS.SB
• DNS Privacy
• DNSlify DNS
• NextDNS
• RethinkDNS
• ControlD
• Mullvad
• OpenBLD.net DNS

## Regional Resolvers
Regional DNS resolvers are typically focused on specific geographic regions, offering optimized performance for users in those areas. These might be run by non-profit organizations, local ISPs, or other entities.

• Yandex DNS
• SWITCH DNS
• SkyDNS RU
• Comss.one DNS
• CIRA Canadian Shield DNS
• OpenNIC DNS -- the IP addresses that are on our pages are dead, and yet the service itself is not. Update with 217.160.70.42, 2001:8d8:1801:86e7::1, mention that this is just one of the available servers, all can be found here: https://servers.opennic.org/
• DNS for Family
• CZ.NIC ODVR
• IIJ.JP DNS
• 114DNS
• Quad101
• OneDNS -- also link the website https://www.onedns.net/
• Applied Privacy DNS
• Fondation Restena DNS
• Digitale Gesellschaft DNS
• LibreDNS

## Small Personal Resolvers
These are DNS resolvers usually run by enthusiasts or small groups. They might not have the scale or redundancy of bigger players, but they often have a strong focus on privacy, transparency, or niche features.

• Privacy-First DNS
• OSZX DNS
• Lelux DNS
• Captnemo DNS
• DNS Forge
• fvz DNS
• FFMUC DNS
• ibksturm DNS
• AhaDNS
• Seby DNS
• Arapurayil
• Dandelion Sprout's Official DNS Server

4. Remove dead resolvers

• DNS.WATCH
• BlahDNS
• FreeDNS
• puntCAT DNS

[anastasiia-fedotova]

We've revamped an article here https://github.com/AdguardTeam/KnowledgeBaseDNS/pull/160. Thanks for your suggestion!