Add ADnull personal DoH resolver

[vitaliit-vvd]

Adding ADnull — a personal DNS-over-HTTPS resolver with ad, tracker and malware blocking.

• DoH URL: https://dns.adnull.com/dns-query
• IPv4: 188.190.191.78 / 188.190.191.52
• Tested with dnscrypt-proxy ✓
• Privacy policy: https://adnull.com/en/privacy-policy

[jedisct1]

I'm not sure that this qualifies as "no logs", especially since the queries seem to be sent to Google.

[jedisct1]

Automated verification results (2026-04-06):

The stamp was tested with dnscrypt-proxy and resolves queries successfully. However, the following issues remain:

1. No-logs claim questioned (unresolved). As noted by @jedisct1 on Mar 29, queries appear to be forwarded to Google, which contradicts the "no logs" property advertised in the stamp (properties flag 0x03). No response from the submitter on this point.

2. No TLS certificate hash. The stamp does not pin any TLS intermediate certificate hash. DoH stamps should include at least one hash for certificate verification.

3. Second IP address missing. The PR description lists two IPs (188.190.191.78 and 188.190.191.52), but only the first appears in the stamp. If both are intended, a second stamp is needed.

4. "Custom subdomain per user account" is mentioned in the description. Per-user subdomains could function as a tracking mechanism, which conflicts with the privacy expectations of this list.

Blocking on issue #1 — the forwarding-to-Google concern needs to be addressed before this can be merged.