docs: update package readmes (#513)

Author: colepeters

packages/core/README.md

@@ -2,16 +2,18 @@
   <a href="https://sanity.io">
     <img src="https://cdn.sanity.io/images/3do82whm/next/1dfce9dde7a62ccaa8e8377254a1e919f6c07ad3-128x128.svg" />
   </a>
-  <h1 align="center">Sanity Core App SDK</h1>
+  <h1 align="center">Sanity App SDK (Core)</h1>
 </p>
 
-Core functionality powering the React SDK.
+The App SDK Core is a pure TypeScript implementation of the App SDK’s business logic. It powers our React App SDK under the hood, and leaves the door open for future framework specific implementations, too.
 
-## Documentation
+We highly recommend that users default to using the hooks provided by the React SDK for building custom apps on the Sanity platform, unless you’re looking to create your own Sanity App SDK using this core layer.
 
-- Familiarize yourself with the App SDK via a conceptual overview, a quickstart guide, and a step by step walkthrough on **[the Sanity Docs site](https://sanity.io/docs/app-sdk)**
-- Go in depth with the **[App SDK reference docs](https://sdk-docs.sanity.dev)**
-- View example implementations on the **[SDK Explorer](https://sdk-examples.sanity.dev)**
+**Looking for our React SDK?** You’ll find it on:
+
+- [GitHub](https://github.com/sanity-io/sdk/tree/main/packages/react)
+- [Sanity Docs](https://sanity.io/docs/app-sdk)
+- [App SDK (React) reference docs](https://reference.sanity.io/_sanity/sdk-react)
 
 ## License
 

packages/react/README.md

@@ -2,16 +2,16 @@
   <a href="https://sanity.io">
     <img src="https://cdn.sanity.io/images/3do82whm/next/1dfce9dde7a62ccaa8e8377254a1e919f6c07ad3-128x128.svg" />
   </a>
-  <h1 align="center">Sanity React App SDK</h1>
+  <h1 align="center">Sanity App SDK (React)</h1>
 </p>
 
 React hooks for creating Sanity applications.
 
 ## Documentation
 
 - Familiarize yourself with the App SDK via a conceptual overview, a quickstart guide, and a step by step walkthrough on **[the Sanity Docs site](https://sanity.io/docs/app-sdk)**
-- Go in depth with the **[App SDK reference docs](https://sdk-docs.sanity.dev)**
-- View example implementations on the **[SDK Explorer](https://sdk-examples.sanity.dev)**
+- Go in depth with the **[App SDK reference docs](https://reference.sanity.io/_sanity/sdk-react)**
+- View example implementations on the **[SDK Explorer](https://sdk-explorer.sanity.io)**
 
 ## License