chore: set up Copilot instructions for Rspack repository

copilot-instructions.md

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+# Rspack - GitHub Copilot Instructions
+
+## Project Overview
+
+Rspack is a high-performance JavaScript bundler written in Rust that offers strong compatibility with the webpack ecosystem. It provides lightning-fast build speeds while allowing seamless replacement of webpack in existing projects.
+
+## Project Architecture
+
+This is a **monorepo** containing both Rust crates and JavaScript packages:
+
+### Rust crates (`crates/`)
+
+- **Core Engine**: Written in Rust for performance
+- **Plugins**: Extensive plugin system (css, javascript, html, etc.)
+- **Bindings**: Node.js bindings through NAPI
+- **Utilities**: Support crates for paths, collections, macros, etc.
+
+### NPM packages  (`packages/`)
+
+- **CLI Tools**: Command-line interface and tooling
+- **API Wrappers**: JavaScript APIs wrapping Rust core
+- **Test Tools**: Testing utilities and frameworks
+- **Create Tools**: Project scaffolding tools
+
+## Development Environment
+
+### Prerequisites
+
+- **Rust**: Uses nightly toolchain (see `rust-toolchain.toml`)
+- **Node.js**: 22+
+- **pnpm**: enforced in `package.json
+
+### Key Commands
+
+```bash
+# Build Rust bindings (development)
+pnpm run build:binding:dev
+
+# Build JavaScript packages  
+pnpm run build:js
+
+# Full development build
+pnpm run build:cli:dev
+
+# Run tests
+pnpm run test:unit      # JavaScript unit tests
+pnpm run test:e2e       # E2E tests
+pnpm run test:webpack   # webpack compatibility tests
+
+# Linting
+pnpm run lint:js        # Linting with Biome
+pnpm run lint:type      # Type checking with Rslint
+```
+
+### File Organization
+
+```
+rspack/
+├── crates/           # Rust source code
+├── packages/         # JavaScript packages
+├── tests/            # Integration tests
+│   ├── webpack-test/ # Webpack compatibility tests
+│   ├── e2e/         # E2E tests
+│   └── bench/       # Benchmarking
+└── website/         # Documentation site
+```
+
+## Contributing Guidelines
+
+- Follow existing code patterns and conventions
+- Add tests for new features
+- Update documentation when changing APIs
+- Run all linters and tests before submitting
+- Use conventional commit messages
+- Keep PRs focused and atomic