Allow config's version to be a path to package.json, closes #2967

Editor assessment

The subject states the feature precisely: the config's version field may now be a path to package.json, with a well-formed closes #2967 footer. The input flexibility, the affected config key, and the implied convenience (single source of truth for versioning) are all evident, so no body is required. The feat type is right, no scope is attached, and no additional footers appear. Hygiene is clean, with the config key identified clearly despite the possessive phrasing. A focused, complete message about a real configuration ergonomics win.