* cli/CI: Improve package.json metadata

The `package.json` contains links for the homepage, the repository, and
a URL to see bugs (although it seems npmjs.com ignores this in favor of
guessing based on the repository being GitHub).

Let's get this metadata right:

* If the project is being auto-published to npmjs.com, ensure the
  metadata is actually set.
* For non-plugins, homepage should point to the project's readme in the
  monorepo rather than https://jetpack.com.
* The `.repository.directory` should always be set.
* The bug URL should point to the project's label, not the combined list
  of all open issues in the whole monorepo.

Co-authored-by: Brandon Kraft <public@brandonkraft.com>

Committed via a GitHub action: https://github.com/Automattic/jetpack/actions/runs/2192193462