Python3 Support with Enhanced Docker and VSCode Integration

This merge request is aimed at integrating Python3 support into the vgtranslate project. It not only brings the project up-to-date with Python3, but also introduces Docker and VSCode configurations for improved development and deployment experience.

Key Features and Changes:

1. Python3 Compatibility: The entire codebase has been migrated to be compatible with Python3.
2. Docker Integration: A Dockerfile and docker-compose.yml have been added to the project, enabling developers to easily containerize the service.
3. VSCode Development Container: For developers using VSCode, a devcontainer setup has been added, streamlining the development environment setup process.
4. Bug Fixes: Resolved a specific bug related to tuple unpacking in the imaging module.
5. Merge Conflicts: Addressed and resolved merge conflicts for a seamless integration with the master branch.

Acknowledgements: A shout-out to @hosterholz for their initial work on the Python3 migration (!2). This MR builds upon their efforts and introduces additional enhancements. However, due to some merge conflicts and the addition of new features, this MR is presented as an alternative to the existing Python3 MR.

Testing: Tests have been conducted on various functionalities to ensure that the migration to Python3 didn't break existing features, and that the Docker integration works as expected.

Request: I kindly request the maintainers and contributors to review the changes and provide feedback. Your insights will be invaluable in ensuring the successful integration of these features into the vgtranslate project.