IPv6 zone index handling

[vapier]

might be getting a little ahead of things, but can we make sure that zone indexes are handled by the spec, even if as a non-normative section ?
https://en.wikipedia.org/wiki/IPv6_address#Scoped_literal_IPv6_addresses_(with_zone_index)

i mention this as it's easy to overlook, and would be nice to have it as part of the initial spec when projects start to implement it to help mitigate.

i don't know if there are other web standards that expose interface level information that could be used as precedence. WebRTC maybe?