docs(engine-server): add deprecation notice to README (#5641)

Author: wjhsf

packages/@lwc/engine-server/README.md

@@ -1,26 +1,7 @@
 # @lwc/engine-server
 
-WARNING: This is an experimental package. It is subject to change, may be removed at any time,
-and should be used at your own risk!
+⚠️ This package is deprecated and has been replaced by [`@lwc/ssr-compiler`](https://www.npmjs.com/package/@lwc/ssr-compiler) and [`@lwc/ssr-runtime`](https://www.npmjs.com/package/@lwc/ssr-compiler).
 
-This package can be used to render LWC components as strings in a server environment.
+## Links
 
-## Supported APIs
-
-This package supports the following APIs.
-
-### renderComponent()
-
-This function renders a string-representation of a serialized component tree, given a tag name
-and an LWC constructor. The output format itself is aligned with the [current leading
-proposal][explainer], but is subject to change.
-
-```js
-import { renderComponent } from '@lwc/engine-server';
-import LightningHello from 'lightning/hello';
-
-const componentProps = {};
-const serialized = renderComponent('lightning-hello', LightningHello, componentProps);
-```
-
-[explainer]: https://github.com/mfreed7/declarative-shadow-dom/blob/master/README.md
+- [Server-Side Rendering guide](https://lwc.dev/guide/ssr)