Add pub badge

Author: olexale

readme.md

@@ -1,5 +1,5 @@
 # Hashids2
-[![Build Status](https://travis-ci.org/olexale/hashids.svg?branch=master)](https://travis-ci.org/olexale/hashids) [![Coverage Status](https://coveralls.io/repos/github/olexale/hashids/badge.svg?branch=master)](https://coveralls.io/github/olexale/hashids?branch=master)
+[![Build Status](https://travis-ci.org/olexale/hashids.svg?branch=master)](https://travis-ci.org/olexale/hashids) [![Coverage Status](https://coveralls.io/repos/github/olexale/hashids/badge.svg?branch=master)](https://coveralls.io/github/olexale/hashids?branch=master) [![pub package](https://img.shields.io/pub/v/hashids2.svg)](https://pub.dartlang.org/packages/hashids2)
 
 A Dart class to generate YouTube-like hashes from one or many numbers.