Switch for special-use domain names
May be Agunua should recognize "special use domain names" (described in RFC 6761) in URL and act accordingly, when the relevant RFC says that applications and libraries could/should do it.
For instance, RFC 6761 says that ".localhost" and ".invalid" can be recognized as special by applications (and immediately ignored, for instance). (On the other end, ".test" and ".example" must be treated as any name.)
RFC 7686 says the application must treat ".onion" as special (and route it to Tor, see #25 (closed)).
This requires to keep track of the special use domain names registry https://www.iana.org/assignments/special-use-domain-names/special-use-domain-names.xml#special-use-domain