Add Docker provider support to TypeScript SDK

[Louis454545]

• Add DockerComputer class with full container lifecycle management
• Implement Docker CLI integration for local development
• Add port mapping for VNC (6901) and API server (8000)
• Support volume mounting for persistent storage and shared directories
• Add container health checking and readiness detection
• Create comprehensive Docker usage example
• Add unit tests for DockerComputer (3 tests passing)
• Update exports to include DockerComputer alongside CloudComputer
• Maintain backward compatibility with existing Computer alias

This brings feature parity with the Python SDK, enabling both cloud and local Docker container support in TypeScript.