Add FANN to the Machine Learning library index (#1840)

* Initial plan

* Add FANN to Machine Learning section

Agent-Logs-Url: https://github.com/fffaraz/awesome-cpp/sessions/c7d20a4b-c188-4588-b561-174888a2edc9

Co-authored-by: fffaraz <895678+fffaraz@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: fffaraz <895678+fffaraz@users.noreply.github.com>

Author: Copilot

README.md

@@ -855,6 +855,7 @@ A curated list of awesome C++ (or C) frameworks, libraries, resources, and shiny
 * [darknet](https://github.com/pjreddie/darknet) - Open source neural network framework written in C and CUDA. [PublicDomain] [website](https://pjreddie.com/darknet/)
 * [Dlib](https://github.com/davisking/dlib) :zap: - A modern C++11 machine learning, computer vision, numerical optimization, and deep learning toolkit. [Boost] [website](http://dlib.net/)
 * [FAISS](https://github.com/facebookresearch/faiss) - A library for efficient similarity search and clustering of dense vectors. [MIT]
+* [FANN](https://github.com/libfann/fann) - Fast Artificial Neural Network library in C. [LGPL]
 * [Fido](https://github.com/FidoProject/Fido) - A highly-modular C++ machine learning library for embedded electronics and robotics. [MIT] [website](http://fidoproject.github.io/)
 * [flashlight](https://github.com/facebookresearch/flashlight) - A fast, flexible machine learning library from Facebook AI Research written entirely in C++ and based on the ArrayFire tensor library. [BSD-3-Clause] [website](https://fl.readthedocs.io/en/latest/)
 * [ggml](https://github.com/ggerganov/ggml) - Tensor library for machine learning with 16-bit and 4-bit quantization support. [MIT]