still need implementation for parsing/output formatting and (perhaps?)
representation (for now, i just followef the ipv4 variant's lead and
am representing it as a tuple of 8x u16).
parsing an ipv6 addr is way more complex than parsing an ipv4 addr, so
i'm putting off an implementation here, for now.
candidate solutions:
- could use getaddrinfo() (exists on both POSIX and windows), but with
incompatible fn signatures.
- libuv has a way to parse an ipv6 string into
a sockaddr_in6, but it also requires a port, so it's probably not aprop
for ip_addr
