improve building process, add size badge

Author: solkimicreb

README.md

@@ -1,6 +1,6 @@
 # React Easy State
 
-[![Build](https://img.shields.io/circleci/project/github/solkimicreb/react-easy-state/master.svg)](https://circleci.com/gh/solkimicreb/react-easy-state/tree/master) [![Coverage Status](https://coveralls.io/repos/github/solkimicreb/react-easy-state/badge.svg)](https://coveralls.io/github/solkimicreb/react-easy-state) [![JavaScript Style Guide](https://img.shields.io/badge/code_style-standard-brightgreen.svg)](https://standardjs.com) [![Version](https://img.shields.io/npm/v/react-easy-state.svg)](https://www.npmjs.com/package/react-easy-state) [![dependencies Status](https://david-dm.org/solkimicreb/react-easy-state/status.svg)](https://david-dm.org/solkimicreb/react-easy-state) [![License](https://img.shields.io/npm/l/react-easy-state.svg)](https://www.npmjs.com/package/react-easy-state)
+[![Build](https://img.shields.io/circleci/project/github/solkimicreb/react-easy-state/master.svg)](https://circleci.com/gh/solkimicreb/react-easy-state/tree/master) [![Coverage Status](https://coveralls.io/repos/github/solkimicreb/react-easy-state/badge.svg)](https://coveralls.io/github/solkimicreb/react-easy-state) [![JavaScript Style Guide](https://img.shields.io/badge/code_style-standard-brightgreen.svg)](https://standardjs.com) [![Package size](http://img.badgesize.io/https://unpkg.com/react-easy-state/dist/esm.es6.min.js?compression=gzip&label=minzip_size)](https://unpkg.com/react-easy-state/dist/esm.es6.js)  [![Version](https://img.shields.io/npm/v/react-easy-state.svg)](https://www.npmjs.com/package/react-easy-state) [![dependencies Status](https://david-dm.org/solkimicreb/react-easy-state/status.svg)](https://david-dm.org/solkimicreb/react-easy-state) [![License](https://img.shields.io/npm/l/react-easy-state.svg)](https://www.npmjs.com/package/react-easy-state)
 
 *Easy State provides a healthy balance of local and global state management in a simple, scalable way.*