Update README.md

Author: mfranzke

README.md

@@ -19,6 +19,11 @@
 
 <!-- ![Pipeline status](https://github.com/db-ui/core/badges/main/pipeline.svg?style=flat) -->
 
+> [!IMPORTANT]
+> We've released the new stable version of the [DB UX Design System v3](https://github.com/db-ux-design-system/core-web), which is the successor of this generation of DB Design Systems.
+> Especially for new projects, we strongly recommend building on [DB UX Design System v3](https://github.com/db-ux-design-system/core-web).
+> The new version has some great benefits and optimisations, especially in terms of accessibility testing, further and better framework support and ongoing development.
+
 > [!WARNING]
 > We've tried a [quick migration to newer SCSS syntax like e.g. `@use` instead of the nowadays deprecated `@import`](https://github.com/db-ui/core/issues/994), but this seems to be more complicated than expected.
 > You might face several warnings on the console when using SASS with our packages regarding `@import` usage. If you'd like to prevent those, you might as well want to evaluate migrating to our newer version of the DB UX Design System: <https://github.com/db-ux-design-system/core-web>