docs(logging): document npm-notice

[darcyclarke]

Summary

We leverage npm-notice to provide information/context from the registry back to the end-user. We should clearly document how & where this messaging comes from in our documentation; making a note that any request to the registry may return a response with a npm-notice header which we then display back to the user.

Exit Criteria

• Add new Logging section to "Using npm" (ref. https://github.com/npm/cli/tree/latest/docs/content/using-npm)
• Document npm-notice & it's usage in the CLI

[darcyclarke]

npm/cli#4113