release: clearly document the requirements to perform a release

Created by: coury-clark

A release captain will need (that I'm aware of):

1. A k8s-dogfood token
2. A github token with repo access
3. A docker hub account
4. Update sg and updated src-cli

Somehow it wasn't entirely clear to me all of the requirements before I started. I'd like these requirements to be clearly documented at the start of the release instructions.