doc: link setRawMode() from signal docs

Fixes: https://github.com/nodejs/node/issues/32065

PR-URL: https://github.com/nodejs/node/pull/32088


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>