Updated readme - link to Rebol/MathPresso extension

Author: Oldes

README.md

@@ -36,6 +36,7 @@ It is possible to extend Rebol functionality using external modules (native and
 * [Rebol/Godot](https://github.com/Oldes/Rebol-Godot) - Extractor of Godot's `.pck` files
 * [Rebol/HTTPd](https://github.com/Oldes/Rebol-HTTPd) - Webserver scheme
 * [Rebol/IRC](https://github.com/Oldes/Rebol-IRC) - Internet Relay Chat scheme
+* [Rebol/MathPresso](https://github.com/Siskin-framework/Rebol-MathPresso) - Mathematical Expression Parser And JIT Compiler
 * [Rebol/Names](https://github.com/Oldes/Rebol-Names) - Random names generator scheme
 * [Rebol/OpenCV](https://github.com/Oldes/OpenCV) - Computer Vision Library
 * [Rebol/SQLite](https://github.com/Siskin-framework/Rebol-SQLite) - SQL database engine