doc: add links for fs.createWriteStream()

Supply links for fs.createWriteStream() in fs.md.

PR-URL: https://github.com/nodejs/node/pull/23104


Reviewed-By: Denys Otrishko <shishugi@gmail.com>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>