force image for social sharing

Author: Flyingmana

README.md

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 # Magento Composer Installer 
 
+<img src="https://getcomposer.org/img/logo-composer-transparent.png" itemprop="image" alt="Dart Mosaic" style="height:50px;">
+
 The purpose of this project is to 
 enable [composer](https://github.com/composer/composer) to install Magento modules,
 and automatically integrate them into a Magento installation.