doc: document behavior of family:0 in dns.lookup()

Fixes: https://github.com/nodejs/node/issues/28159

PR-URL: https://github.com/nodejs/node/pull/28163


Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>