docs: add a CONTRIBUTING.md with build instruction

Author: davidB

CONTRIBUTING.md

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+# Contributing to tracing-opentelemetry-instrumentation-sdk
+
+Thank you for your interest in contributing! This document provides guidelines and instructions for setting up your development environment and contributing to the project.
+
+## Development Environment Setup
+
+### Prerequisites
+
+1. **Install mise** (if not already installed):
+
+   ```bash
+   # Using the install script
+   curl https://mise.run | sh
+
+   # Or using a package manager
+   # macOS: brew install mise
+   # Arch: pacman -S mise
+   # Ubuntu/Debian: see https://mise.jdx.dev/installing-mise.html
+   ```
+
+2. **Clone the repository**:
+
+   ```bash
+   git clone https://github.com/davidB/tracing-opentelemetry-instrumentation-sdk.git
+   cd tracing-opentelemetry-instrumentation-sdk
+   ```
+
+3. **Install tools and dependencies**:
+
+   ```bash
+   # Install all tools defined in .mise.toml (Rust, protoc, grpcurl, etc.)
+   mise install
+
+   # Activate the environment (or use 'mise use' for shell integration)
+   mise activate
+   ```
+
+### Available Development Tasks
+
+We use `mise` tasks for all development workflows. Here are the main tasks:
+
+#### Code Quality & Formatting
+
+```bash
+# Format code
+mise run format
+
+# Lint code (clippy + format check)
+mise run lint
+
+# Check code with all feature combinations
+mise run check
+
+# Run cargo deny security checks
+mise run deny
+```
+
+#### Testing
+
+```bash
+# Run tests (using nextest + doctests)
+mise run test
+
+# Test each feature separately (slower but thorough)
+mise run test-each-feature
+```
+
+#### Tool Installation
+
+These tasks automatically install required tools if not present:
+
+```bash
+# Individual tool installation (usually handled automatically by other tasks)
+mise run install:cargo-hack
+mise run install:cargo-nextest
+mise run install:cargo-insta
+mise run install:cargo-deny
+```
+
+#### Container & Examples
+
+```bash
+# Start Jaeger all-in-one for local development
+mise run run-jaeger
+
+# Run example applications
+mise run run-example-grpc-server     # gRPC server example
+mise run run-example-grpc-client     # gRPC client example
+mise run run-example-axum-otlp-server # Axum HTTP server
+mise run run-example-http-client     # HTTP client test
+mise run run-example-load            # Load testing example
+```
+
+#### Version Management
+
+```bash
+# Set version across all workspace crates
+mise run set-version 0.1.0
+```
+
+### Development Workflow
+
+1. **Setup environment** (first time only):
+
+   ```bash
+   mise install
+   ```
+
+2. **Before making changes**:
+
+   ```bash
+   # Format and check code
+   mise run format
+   mise run lint
+   mise run check
+   ```
+
+3. **While developing**:
+
+   ```bash
+   # Run tests frequently
+   mise run test
+
+   # Test with examples if relevant
+   mise run run-jaeger &  # Start Jaeger in background
+   mise run run-example-axum-otlp-server
+   ```
+
+4. **Before submitting PR**:
+   ```bash
+   # Full validation
+   mise run format
+   mise run lint
+   mise run check
+   mise run test
+   mise run deny
+   ```
+
+### Testing with OpenTelemetry
+
+#### Local Jaeger Setup
+
+```bash
+# Start Jaeger (runs on various ports including 16686 for UI, 4317/4318 for OTLP)
+mise run run-jaeger
+
+# Open Jaeger UI
+open http://localhost:16686
+```
+
+#### Running Examples
+
+```bash
+# Terminal 1: Start Jaeger
+mise run run-jaeger
+
+# Terminal 2: Start example server
+mise run run-example-axum-otlp-server
+
+# Terminal 3: Send requests and check traces
+mise run run-example-http-client
+# Then check traces in Jaeger UI at http://localhost:16686
+```
+
+### Project Structure
+
+This workspace contains several crates:
+
+- **`init-tracing-opentelemetry/`**: Helpers to initialize tracing + opentelemetry
+- **`axum-tracing-opentelemetry/`**: Axum middlewares for tracing integration
+- **`tonic-tracing-opentelemetry/`**: Tonic (gRPC) middlewares for tracing
+- **`tracing-opentelemetry-instrumentation-sdk/`**: Core instrumentation SDK
+- **`fake-opentelemetry-collector/`**: Testing utilities and fake collector
+- **`testing-tracing-opentelemetry/`**: Test utilities
+- **`examples/`**: Working examples demonstrating usage
+
+### Code Style & Guidelines
+
+- **Formatting**: We use `rustfmt` with default settings
+- **Linting**: All clippy warnings must be addressed
+- **Testing**: Add tests for new functionality
+- **Documentation**: Update documentation for public APIs
+- **Examples**: Update examples if adding new features
+
+### Continuous Integration
+
+Our CI pipeline runs:
+
+- `mise run check` - Feature compatibility checks
+- `mise run lint` - Code formatting and clippy
+- `mise run test` - Full test suite
+- `mise run deny` - Security and license checks
+
+Make sure all these pass locally before submitting a PR.
+
+### Common Issues & Solutions
+
+#### Tool Installation Issues
+
+If tools fail to install automatically:
+
+```bash
+# Install cargo-binstall manually
+curl -L --proto '=https' --tlsv1.2 -sSf https://raw.githubusercontent.com/cargo-bins/cargo-binstall/main/install-from-binstall-release.sh | bash
+
+# Then retry the task
+mise run <task-name>
+```
+
+#### Container Runtime
+
+The project supports multiple container runtimes (podman, nerdctl, docker). If you have issues:
+
+```bash
+# Make sure one of these is installed and available
+which podman || which nerdctl || which docker
+```
+
+#### Environment Variables
+
+Key environment variables (already set in `.mise.toml`):
+
+- `OTEL_EXPORTER_OTLP_TRACES_ENDPOINT="http://127.0.0.1:4317"`
+- `OTEL_EXPORTER_OTLP_TRACES_PROTOCOL="grpc"`
+- `OTEL_TRACES_SAMPLER="always_on"`
+
+### Getting Help
+
+- Check existing [issues](https://github.com/davidB/tracing-opentelemetry-instrumentation-sdk/issues)
+- Review the [examples/](examples/) directory for usage patterns
+- Look at test files for API usage examples
+- Open a new issue for bugs or feature requests
+
+### Submitting Changes
+
+1. Fork the repository
+2. Create a feature branch: `git checkout -b feature/my-new-feature`
+3. Make your changes following the guidelines above
+4. Run the full test suite: `mise run lint && mise run test && mise run deny`
+5. Commit with descriptive messages
+6. Push to your fork and submit a pull request
+
+Thank you for contributing!