docs(storybook): add documentation to filter s2 components (#4155)

Author: marissahuysentruyt

.storybook/guides/s2_migration.mdx

@@ -13,6 +13,10 @@ import GrayMigrationGuide from "../assets/images/gray_migration-guide.png";
 - Search within: Use a search field with a separate control to filter the search instead.
 - Split button: Use a button group to show any additional actions related to the most critical action. Reference [Spectrum documentation](https://spectrum.corp.adobe.com/page/button-group/#Use-a-button-group-to-show-additional-actions) for more information.
 
+## Migrated components
+
+You can find a list of components that have been fully migrated to Spectrum 2 by filtering the components by the `migrated` tag. In the Storybook search field, click the filter button and select the `migrated` checkbox. The list of components should update to display only components that have been tagged as migrated.
+
 ## Grays
 
 <img