doc: add Gibson Fahnestock to Release team

Refs: https://github.com/nodejs/TSC/issues/350

You can check by running the command below:

 gpg --keyserver pool.sks-keyservers.net --recv-keys 77984A986EBC2AA786BC0F66B01FBB92821C587A 

And making sure it actually works.

cc/ @nodejs/release @nodejs/lts

CI: https://ci.nodejs.org/job/node-test-commit/13610/