Improve `CONTRIBUTING.md` (#58396)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/58396
Test Plan: Imported from OSS
Reviewed By: samestep
Differential Revision: D28476510
Pulled By: ansley
fbshipit-source-id: 3f45bee93dfeda06a44570305f9699bcafc45d2e
