Add badges.

Author: Ned Zimmerman

README.md

@@ -1,3 +1,5 @@
 # Pressbooks Build Tools
 
+[![npm](https://img.shields.io/npm/v/pressbooks-build-tools.svg?style=flat-square)](https://www.npmjs.com/package/pressbooks-build-tools) [![GitHub release](https://img.shields.io/github/release/pressbooks/pressbooks-build-tools.svg?style=flat-square)](https://github.com/pressbooks/pressbooks-build-tools/releases/latest)
+
 NPM package which includes all asset linting and build tools for Pressbooks projects.