docs: update README

README.md

@@ -2,6 +2,11 @@
 
 Hono DO is a wrapper of [Cloudflare Workers](https://workers.cloudflare.com/) ' [Durable Object](https://developers.cloudflare.com/workers/learning/using-durable-objects), designed for [Hono](https://hono.dev/).
 
+> [!IMPORTANT]
+> Cloudflare released [RPC](https://developers.cloudflare.com/workers/runtime-apis/rpc/) feature, which is a better way to communicate between Durable Objects.
+> This library was developed to improve the developer experience for Durable Objects when RPC was not yet available.
+> So, please consider it before using this library.
+
 ```bash
 $ npm install hono-do
 ```