Have completed chapter2 extended challenge and would like to contribute code back

[srinathln7]

Hi @tnballo,
Thank you for starting this incredible book. It perfectly aligns with my interests in systems programming, software security, and Rust. I understand that the book is currently not under active development, but I would like to contribute some code, starting with the extended challenge and accompanying test cases for Chapter2: https://github.com/srinathln7/rc4/tree/main/rcli

I am eager to contribute to the future development of this book in any way I can. If you would like me to open a PR for the mentioned code, I would be happy to do so. Please let me know. Hope, you get to find some time in the future to continue this adventure.