Add romeric/Fastor to the Math section in README (#1771)

* Initial plan

* Add Fastor to Math libraries list

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

* Update Fastor description wording

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

@@ -879,6 +879,7 @@ A curated list of awesome C++ (or C) frameworks, libraries, resources, and shiny
 * [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/)
 * [Eigen](http://eigen.tuxfamily.org/) - A high-level C++ library of template headers for linear algebra, matrix and vector operations, numerical solvers and related algorithms. [MPL2]
 * [ExprTk](https://www.partow.net/programming/exprtk/) - The C++ Mathematical Expression Toolkit Library (ExprTk) is a simple to use, easy to integrate and extremely efficient run-time mathematical expression parser and evaluation engine. [MIT]
+* [Fastor](https://github.com/romeric/Fastor) - A lightweight high performance tensor algebra framework for modern C++. [MIT]
 * [Geometric Tools](https://www.geometrictools.com) - C++ library for computing in the fields of mathematics, graphics, image analysis and physics. [Boost] [website](https://www.geometrictools.com)
 * [GLM](https://github.com/g-truc/glm) - Header-only C++ math library that matches and inter-operates with OpenGL's GLSL math. [MIT] [website](https://glm.g-truc.net/)
 * [GMTL](http://ggt.sourceforge.net/) - Graphics Math Template Library is a collection of tools implementing Graphics primitives in generalized ways. [GPL2]