docs: add PyPI monthly downloads badge

[ulises-jeremias]

Summary

• Adds a PyPI Downloads badge (monthly, via shields.io dm endpoint) to both the monorepo root README.md and the package-level packages/create-awesome-python-app/README.md
• Badge is placed immediately after the existing PyPI version badge for visual grouping
• Uses the same shields.io style as the rest of the package-level badges (flat-square)

Badge preview

[![PyPI Downloads](https://img.shields.io/pypi/dm/create-awesome-python-app.svg)](https://pypi.org/project/create-awesome-python-app/)

🤖 Generated with Claude Code