Gatsby Development CLI

`gatsby-dev-cli` is a command-line interface tool specifically designed to assist contributors in the local development and testing of the Gatsby core framework. Its primary function is to enable developers to link a local clone of the Gatsby monorepo to a Gatsby site, allowing changes made to Gatsby packages to be copied directly into the site's `node_modules` for immediate, real-time testing. After the initial copy, the tool can maintain a watch task to automatically re-copy any changed modules, streamlining the iterative development process. The current stable version is 5.16.0. Gatsby generally follows a continuous release cadence for minor fixes and features within a major version, with major versions released less frequently. This CLI's key differentiation lies in its ability to facilitate rapid iteration on Gatsby core features directly within a consuming project, bypassing the complexities of manual `npm link` or copying. It is an essential utility for anyone contributing to the Gatsby project itself.