This PR adds a new documentation file, docker/docs_docker-quickstart_Version2.md, which provides clear, step-by-step instructions for running doccano using Docker and Docker Compose. The guide includes:

• How to build and start all necessary services (backend, frontend, Celery worker, Redis) with Docker Compose
• Creating a superuser using Docker
• Ensuring that the Celery worker is running so that the export functionality works
• Troubleshooting tips for export issues

This documentation is intended to help new users and contributors set up a working doccano environment quickly, especially those who rely on Docker for development and deployment.

If you have any suggestions or would like further clarification in the docs, please let me know!