Add `povils/phpmnd`

Co-authored-by: Povilas Susinskas <povilas.susinskas@gmail.com>

README.md

 * [Better Reflection](https://github.com/Roave/BetterReflection) - AST-based reflection library that allows analysis and manipulation of code
 * [Code Climate](https://codeclimate.com) - An automated code review.
 * [GrumPHP](https://github.com/phpro/grumphp) - A PHP code-quality tool.
+* [PHP Magic Number Detector](https://github.com/povils/phpmnd) - A library that detects magic numbers in code.
 * [PHP Parser](https://github.com/nikic/PHP-Parser) - A PHP parser written in PHP.
 * [PHP Semantic Versioning Checker](https://github.com/tomzx/php-semver-checker) - A command line utility that compares two source sets and determines the appropriate semantic versioning to apply.
 * [Phpactor](https://github.com/phpactor/phpactor) - PHP completion, refactoring and introspection tool.