doc: better linkage to node-addon-api

One of the comments we got at the N-API workshop
at NodeConfEU was that we should have a better link to
node-addon-api and the docs in the main API docs for
N-API. The goal being to help people find node-addon-api
and potentially start with the node-addon-api docs
instead if they are using C++.

This expands and strengthens the link along with a
recommendation that starting with the node-addon-api
docs might make sense.

PR-URL: https://github.com/nodejs/node/pull/24371


Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>