Add pyproject.toml for modern Python packaging

Describe the enhancement

The mssql-python project currently uses setup.py for packaging configuration. Modern Python packaging standards recommend using pyproject.toml as the primary configuration file for build systems, dependencies, and project metadata. This change would improve maintainability, standardize the build process, and align with current Python packaging best practices.

Benefits of migrating to pyproject.toml

1. Modern Standard: pyproject.toml is the current standard defined by PEP 518, PEP 621, and PEP 660
2. Declarative Configuration: Cleaner, more readable configuration format
3. Tool Integration: Better support for development tools (black, flake8, pytest, mypy, etc.)
4. Build System Isolation: Proper build dependency specification
5. IDE Support: Enhanced IDE integration and tooling support

Proposed changes

• Create pyproject.toml with project metadata - refer https://peps.python.org/pep-0621/

Referenced from #242 on versioning discussion