Update README.md

Author: coderdiaz

README.md

@@ -15,6 +15,7 @@
     <a href="https://github.com/coderdiaz/vue-datasource/stargazers"><img src="https://img.shields.io/github/stars/coderdiaz/vue-datasource.svg?style=flat-square"></a>
     <a href="http://npmjs.com/package/vue-datasource"><img src="https://img.shields.io/npm/v/vue-datasource.svg?style=flat-square"></a>
     <a href="http://npmjs.com/package/vue-datasource"><img src="https://img.shields.io/npm/dm/vue-datasource.svg?style=flat-square"></a>
+    <a href="https://www.paypal.me/coderdiaz"><img src="https://img.shields.io/badge/invite-coffee-red.svg?style=flat-square"></a>
 </p>
 
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