doc: add `socket.readyState`

+ description of `socket.readyState`

Note: YAML tag found in commit e697cfb6



Co-authored-by: Michael Auderer <mike@silverstone.io>

PR-URL: https://github.com/nodejs/node/pull/35262


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>