Update GOVERNANCE.md (#1082)

* Update GOVERNANCE.md

Follow up nodejs/node#57311 (comment)

* Update GOVERNANCE.md

Co-authored-by: Antoine du Hamel <duhamelantoine1995@gmail.com>

---------

Co-authored-by: Antoine du Hamel <duhamelantoine1995@gmail.com>

Author: RafaelGSS

GOVERNANCE.md

@@ -159,6 +159,9 @@ After the nominee's first prepared release has been promoted, the new releaser m
 * Open a PR in [nodejs/release-keys](https://github.com/nodejs/release-keys) to add their GPG key via `./cli.sh add $KEY_ID`.
 * Open a PR in [nodejs/Release](https://github.com/nodejs/Release) to add themselves under the "Releasers team" heading via `ncu-team sync README.md`.
 * Add them to the `#nodejs-release-private` team on the OpenJS Slack.
+* Configure git to sign all backport commits and release commits with the GPG key used to
+  sign the releases. Consider signing all commits on your local clone, e.g. with the
+  following command: `git config commit.gpgsign true`.
 
 New releasers should wait at least 2 weeks after adding a GPG key to the
 nodejs/node README credentials before signing a release.