Add note on wrangler v2 support (#6639)

Author: lrapoport-cf

packages/wrangler/README.md

@@ -8,6 +8,10 @@
 
 `wrangler` is a command line tool for building [Cloudflare Workers](https://workers.cloudflare.com/).
 
+> [!WARNING]
+>
+> Wrangler v2 is **only receiving critical security updates.** We recommend you [migrate to Wrangler v3](https://developers.cloudflare.com/workers/wrangler/migration/update-v2-to-v3/) if you can.
+
 ## Quick Start
 
 ```bash