📝 Update README.md

Author: Anthony Du Pont

README.md

@@ -3,6 +3,7 @@
 [![Travis](https://img.shields.io/travis/Dogstudio/highway.svg)](https://travis-ci.org/Dogstudio/highway)
 [![npm](https://img.shields.io/npm/v/@dogstudio/highway.svg)](https://www.npmjs.com/package/@dogstudio/highway)
 [![npm](https://img.shields.io/npm/dt/@dogstudio/highway.svg)](https://www.npmjs.com/package/@dogstudio/highway)
+[![Gzip Size](https://img.badgesize.io/https://unpkg.com/@dogstudio/[email protected]/dist/highway.min.js?compression=gzip)](https://unpkg.com/@dogstudio/[email protected]/dist/highway.min.js)
 [![Test Coverage](https://api.codeclimate.com/v1/badges/230e0c2e5e924edfe341/test_coverage)](https://codeclimate.com/github/Dogstudio/highway/test_coverage)
 [![GitHub issues](https://img.shields.io/github/issues-raw/Dogstudio/highway.svg)](https://github.com/Dogstudio/highway/issues)