Add book recommendation to README

Added a link to the book 'Crack Any Codebase with AI' in the README.

Author: zachary62

README.md

@@ -14,13 +14,17 @@
 
 This is a tutorial project of [Pocket Flow](https://github.com/The-Pocket/PocketFlow), a 100-line LLM framework. It crawls GitHub repositories and builds a knowledge base from the code. It analyzes entire codebases to identify core abstractions and how they interact, and transforms complex code into beginner-friendly tutorials with clear visualizations.
 
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+- Check out the [book "Crack Any Codebase with AI"](https://www.manning.com/books/crack-any-codebase-with-ai) for more! 
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 - Check out the [YouTube Development Tutorial](https://youtu.be/AFY67zOpbSo) for more!
 
 - Check out the [Substack Post Tutorial](https://zacharyhuang.substack.com/p/ai-codebase-knowledge-builder-full) for more!
 
   **🔸 🎉 Reached Hacker News Front Page** (April 2025) with >900 up‑votes:  [Discussion »](https://news.ycombinator.com/item?id=43739456)
 
 
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 ## ⭐ Example Results for Popular GitHub Repositories!
 
 <p align="center">