chore: fix README link to npm (#17964)

Author: andrewseguin

README.md

@@ -1,5 +1,5 @@
 # Official components for Angular
-[![npm version](https://badge.fury.io/js/%40angular%2Fcdk.svg)](https://www.npmjs.com/package/%40angular%cdk)
+[![npm version](https://badge.fury.io/js/%40angular%2Fcdk.svg)](https://www.npmjs.com/package/@angular/cdk)
 [![Build status](https://circleci.com/gh/angular/components.svg?style=svg)](https://circleci.com/gh/angular/components)
 [![Gitter](https://badges.gitter.im/angular/components.svg)](https://gitter.im/angular/material2?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge)