docs: badge label [skip ci]

Author: adhocore

readme.md

@@ -8,7 +8,9 @@ PHP underscore inspired &/or cloned from awesome `_.js`. A set of utilities
 [![Codecov branch](https://img.shields.io/codecov/c/github/adhocore/php-underscore/master.svg?style=flat-square)](https://codecov.io/gh/adhocore/php-underscore)
 [![StyleCI](https://styleci.io/repos/108437038/shield)](https://styleci.io/repos/108437038)
 [![Software License](https://img.shields.io/badge/license-MIT-brightgreen.svg?style=flat-square)](LICENSE)
-[![Donate](https://img.shields.io/badge/donate-paypal-blue.svg?style=flat-square)](https://www.paypal.me/ji10/50usd)
+[![Donate 15](https://img.shields.io/badge/donate-paypal-blue.svg?style=flat-square&label=donate+15)](https://www.paypal.me/ji10/15usd)
+[![Donate 25](https://img.shields.io/badge/donate-paypal-blue.svg?style=flat-square&label=donate+25)](https://www.paypal.me/ji10/25usd)
+[![Donate 50](https://img.shields.io/badge/donate-paypal-blue.svg?style=flat-square&label=donate+50)](https://www.paypal.me/ji10/50usd)
 [![Tweet](https://img.shields.io/twitter/url/http/shields.io.svg?style=social)](https://twitter.com/intent/tweet?text=Functional+programming+paradigm+in+PHP+to+manipulate+arrays+like+pro&url=https://github.com/adhocore/php-underscore&hashtags=php,functional,array,collection)