Modified the README file to reflect the transition from development to a stable phase and removed the roadmap. Also, renamed `sidebar.config.ts` to `navigation.config.ts` for more clarity. Additionally, added `.zed` to `.gitignore` to prevent commit of unneeded files.
Environment variable definitions were moved from .env.development, .env.test and .env.production to a new shared .env file. This provides a centralized location for common environment variables values, easier manageability, and overrides capability in specific environments. The .gitignore file was also updated to no longer ignore the .env file as this file now contains public / non-sensitive configuration values.
