Add composer-unused (#1086)

* Add composer-unused

Add composer-unused in `Dependency Manager Extras`-Section.
This is a small CLI Tool which scans you `composer.json` of any unused package by doing a static analysis of used symbols in your code.

URL: https://github.com/composer-unused/composer-unused

* Add composer require checker

Co-authored-by: Jamie York <ziadoz@gmail.com>

README.md

 * [Composed](https://github.com/joshdifabio/composed) - A library to parse your project's Composer environment at runtime.
 * [Composer Merge Plugin](https://github.com/wikimedia/composer-merge-plugin) - A composer plugin to merge several composer.json files.
 * [Composer Patches](https://github.com/cweagans/composer-patches) - A plugin for Composer to apply patches.
+* [Compoer Require Checker](https://github.com/maglnet/ComposerRequireChecker) - CLI tool to analyze composer dependencies and verify that no unknown symbols are used in the sources of a package.
+* [Composer Unused](https://github.com/composer-unused/composer-unused) - A CLI Tool to scan for unused composer packages.
 * [Prestissimo](https://github.com/hirak/prestissimo) - A composer plugin which enables parallel install process.
 * [Repman](https://repman.io) - A private PHP package repository manager and Packagist proxy.
 * [Satis](https://github.com/composer/satis) - A static Composer repository generator.