Add 'is' command alias and PyPI deployment instructions

[Copilot]

This PR makes the interactive-sort package fully pip installable with two command-line entry points as requested in the issue.

Changes Made

1. Added is command alias

Updated pyproject.toml to include a short alias for the interactive sorting tool:

[project.scripts]
interactive-sort = "interactive_sort.main:main"
is = "interactive_sort.main:main"

After installation, users can now run the tool using either command:

• interactive-sort [OPTIONS] - Full command name
• is [OPTIONS] - Short alias for convenience

Both commands are functionally identical and provide the same interactive sorting experience with real-time display.

2. Created comprehensive deployment guide

Added DEPLOY.md with step-by-step instructions for building and uploading the package to PyPI, including:

• Prerequisites and setup (build tools, PyPI credentials)
• Building distribution files with python -m build
• Testing the build locally before deployment
• Uploading to Test PyPI first, then production
• Version management guidelines
• Reference for both available commands

Package Status

The package was already properly structured for pip installation with modern pyproject.toml configuration. This PR simply adds the requested second command and deployment documentation. The package is now ready for distribution to PyPI following the instructions in DEPLOY.md.

Fixes #7.

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