Add QArt

README.md

 * [Intervention Image](https://github.com/Intervention/image) - Another image manipulation library.
 * [PHP Image Workshop](https://github.com/Sybio/ImageWorkshop) - Another image manipulation library.
 * [PHP QR Code](https://github.com/chillerlan/php-qrcode/) - QR Code generator and reader.
+* [QArt](https://github.com/mikaelcarlavan/qart-php) - A generator for QR codes that embed an image as a colour halftone.
 
 ### Testing
 *Libraries for testing codebases and generating test data.*