Set up test framework and project structure

[github-actions]

Test Framework Setup

Description

Set up the basic project structure and testing framework for the Arithmetic Python library.

Acceptance Criteria

• Create basic Python package structure with __init__.py
• Set up pytest as the testing framework
• Create requirements.txt or pyproject.toml for dependencies
• Create tests/ directory with appropriate structure
• Ensure tests can be run with pytest command
• Set up basic CI/CD configuration (if applicable)

Files to Create/Modify

• arithmetic/__init__.py
• tests/__init__.py
• requirements.txt or pyproject.toml
• Test configuration files as needed

Testing Requirements

• Verify that pytest runs without errors (even with no tests initially)
• Confirm package can be imported correctly