Add npm shields

Author: kriskbx

readme.md

@@ -2,6 +2,9 @@
 
 > A command line interface that makes working with GitLabs time tracking feature more enjoyable.
 
+[![npm](https://img.shields.io/npm/dt/gitlab-time-tracker.svg?style=flat-square)](https://www.npmjs.com/package/gitlab-time-tracker)
+[![npm](https://img.shields.io/npm/v/gitlab-time-tracker.svg?style=flat-square)](https://www.npmjs.com/package/gitlab-time-tracker)
+
 ![preview](https://raw.githubusercontent.com/kriskbx/gitlab-time-tracker/master/preview.gif)
 
 ### requirements