safeurl: Missing IPv6 CIDR Ranges in Blocklist

safeurl is a server-side request forgery protection library. Prior to 0.2.4, the privateNetworks list in ip.go omits the IPv6 ranges 64:ff9b:1::/48, 5f00::/16, 3fff::/20, and 100:0:0:1::/64. When an application enables IPv6 with EnableIPv6(true), an attacker-controlled destination in one of these ranges is not recognized as non-public and can pass the SSRF destination check, potentially allowing access to resources hosted within the omitted ranges. IPv6 is disabled by default, and configurations that retain EnableIPv6(false) are not exposed to this bypass. This issue is fixed in version 0.2.4.