and fix outdated statements along the way

Old version suggested Kubo RPC is "IPFS RPC".

This refactor moves Kubo RPC and CLI under `/reference/kubo/`
while ensuring we don't break existing websites linking to specific RPC
command docs, and orchestration responsible for updating docs continues
working under the new paths.

A placeholder for HTTP Gateway reference is added, as we want people to
default to Gateway API and use implementation-specific RPC only when
generic Gateway interface is not enough.

Vuepress was ignoring inlinded JS outside dev mode. This refactors the
way advanced redirect is done to always work.

Renamed everything to kubo.
(curl was not following redirects, so it would fail anyway)

Replaces placeholder with basic information about the API
and points at follow-up resources (how-tos, specs)