README: Add Storybook badge (#66529)

* README: Add Storybook badge

* Add alt tag

Co-authored-by: tyxla <[email protected]>
Co-authored-by: mirka <[email protected]>

Author: tyxla

README.md

@@ -7,6 +7,8 @@
 [![React Native E2E Tests (iOS)](<https://github.com/WordPress/gutenberg/workflows/React%20Native%20E2E%20Tests%20(iOS)/badge.svg>)](https://github.com/WordPress/gutenberg/actions?query=workflow%3A%22React+Native+E2E+Tests+%28iOS%29%22+branch%3Atrunk)
 [![React Native E2E Tests (Android)](<https://github.com/WordPress/gutenberg/workflows/React%20Native%20E2E%20Tests%20(Android)/badge.svg>)](https://github.com/WordPress/gutenberg/actions?query=workflow%3A%22React+Native+E2E+Tests+%28Android%29%22+branch%3Atrunk)
 
+<a href="https://wordpress.github.io/gutenberg/" target="_blank"><img src="https://raw.githubusercontent.com/storybooks/brand/master/badge/badge-storybook.svg" alt="Storybook Badge" /></a>
+
 [![lerna](https://img.shields.io/badge/maintained%20with-lerna-cc00ff.svg)](https://lerna.js.org)
 
 ![Screenshot of the Gutenberg Editor, editing a post in WordPress](https://user-images.githubusercontent.com/1204802/100067796-fc3e8700-2e36-11eb-993b-6b80b4310b87.png)