Storybook: update docs to clarify the absence of polyfills

storybook/stories/docs/introduction.story.mdx

@@ -33,6 +33,10 @@ To use it in your local development environment run the following command in the
  npm run storybook:dev
  ```
 
+## Additional notes
+
+Please note that **polyfills are not loaded in Storybook** (unlike what happens in the Gutenberg app). As a result, certain components may not work as expected depending on which browser is being used to view the interactive stories.
+
 ## Resources to learn more:
 
 - [Storybook.js.org](https://storybook.js.org/) - Storybook is a frontend workshop for building UI components and pages in isolation.