add GPT.c port to README.md

[MYusufY]

Hello!

First, I just want to say that this project is really inspiring. As a 13 year-old developer, I’ve learned a lot from reading the code.

As a weekend project, I created a custom GPT-like version of Llama2.c.
Initially, my goal was to build a pure C inference engine for nanoGPT models (similar to Llama2.c), but the project evolved quickly and I ended up making a custom GPT-style implementation instead. The nanoGPT support is still experimental, but I plan to add a more stable export option for it soon.

My main focus now is implementing GPT.c on ESP32, like existing Llama2.c ports such as this one.

Would it be okay to add this project to the list of forks in the README? I think it could be useful for others interested in GPT-like versions.

Thanks again for your great work and contributions to open-source AI!