Docs: Cross-link Testing Overview from Storybook README

storybook/README.md

@@ -8,3 +8,8 @@ View online at: https://wordpress.github.io/gutenberg/
 
 Run locally in your development environment running: `npm run storybook:dev` from the top-level Gutenberg directory.
 
+## StoryShots Integration
+
+> [StoryShots](https://www.npmjs.com/package/@storybook/addon-storyshots) adds automatic Jest Snapshot Testing for [Storybook](https://storybook.js.org/).
+
+Please refer to [Testing Overview](/docs/contributors/testing-overview.md#storyshots) to learn how to maintain auto-generated unit tests from stories added to Storybook.