added flake.nix and direnv dev environment for nix users also made a

[conneroisu]

This pull request introduces a Nix-based development environment for the CCManager project. The changes include the addition of a flake.nix file to define the environment and modifications to .envrc to integrate with nix-direnv. These updates aim to streamline development workflows, ensure reproducibility, and provide cross-platform compatibility.

Development Environment Setup:

• Added a flake.nix file to define the CCManager development environment, including dependencies, build configurations, and shell setup. This includes support for both Linux and macOS-specific build tools, environment variables, and convenience aliases for common commands like npm run dev, npm run build, and npm test.
• Configured a development shell with tools like Node.js, TypeScript, Prettier, ESLint, and Git, as well as native build tools for handling Node.js native modules.

Integration with nix-direnv:

• Updated .envrc to check for and source the appropriate version of nix-direnv (v3.0.6) and enable the use of flakes. This ensures seamless integration with the Nix development environment.