docs(readme): add npm badge [ci skip]

Author: Eric Liu

README.md

@@ -1,5 +1,6 @@
 # carbon-icons-svelte
 
+[![NPM][npm]][npm-url]
 [![Build][build]][build-badge]
 [![Coverage][codecov-shield]][codecov]
 
@@ -43,6 +44,8 @@ For faster compile times, import icons individually:
 
 [Apache 2.0](LICENSE)
 
+[npm]: https://img.shields.io/npm/v/carbon-icons-svelte.svg?color=blue
+[npm-url]: https://npmjs.com/package/carbon-icons-svelte
 [build]: https://travis-ci.com/ibm/carbon-icons-svelte.svg?branch=master
 [build-badge]: https://travis-ci.com/ibm/carbon-icons-svelte
 [codecov]: https://codecov.io/gh/ibm/carbon-icons-svelte