(docs) add bundle size badge

Author: antoine92190

README.md

@@ -1,5 +1,6 @@
 <p align="center">
   <a href="https://www.npmjs.com/package/vue-advanced-chat"><img src="https://img.shields.io/npm/dm/vue-advanced-chat.svg"></a>
+  <a href="https://www.npmjs.com/package/vue-advanced-chat"><img src="https://img.shields.io/bundlephobia/minzip/vue-advanced-chat"></a>
   <a href="https://www.npmjs.com/package/vue-advanced-chat"><img src="https://img.shields.io/npm/v/vue-advanced-chat.svg"></a>
   <a href="https://www.npmjs.com/package/vue-advanced-chat"><img src="https://img.shields.io/npm/l/vue-advanced-chat.svg"></a>
 </p>