Introducing environment variable support for Sanity Studio

Sanity Studio now supports environment variables, enhancing continuous integration (CI) capabilities and simplifying the deployment of studios for various projects and datasets from a unified codebase, along with enabling environment-specific customizations. As an open-source editing platform that connects with Sanity's hosted datastore, Sanity Studio allows direct deployment from a local machine, but users often prefer to commit code to git and establish a deployment workflow, a method also favored by Sanity. Users can access the new feature by upgrading their Sanity Studio and referring to the documentation for guidance.