Add note about v2 (#2380)

* add note about the next iteration

* Update README.md

Co-authored-by: May Lee <[email protected]>

* add note about migration.md

---------

Co-authored-by: May Lee <[email protected]>

Author: skarimo

README.md

@@ -1,3 +1,8 @@
+> [!NOTE]
+> The next major version iteration of `@datadog/datadog-api-client`, `v2`, is now in Preview.
+> The `v2` splits the monolithic client into new logically grouped api package structure.
+> See [MIGRATION.md](https://github.com/DataDog/datadog-api-client-typescript/blob/v2/MIGRATION.md) and the [`v2` branch](https://github.com/DataDog/datadog-api-client-typescript/tree/v2) branch for more details.
+
 # Node.js Datadog API Client
 
 [![License](https://img.shields.io/badge/License-Apache%202.0-blue.svg)](https://opensource.org/licenses/Apache-2.0)