Update readme.md

Update readme with details on how to extend type

Author: DanielRivers

readme.md

@@ -17,12 +17,24 @@ pnpm install @kinde/jwt-decoder
 
 ## Usage
 
-```js
+__import function__
+```ts
 import { jwtDecoder } from "@kinde/jwt-decoder";
+```
 
+__Simple decode__
+```ts
 const decodedToken = jwtDecoder("eyJhbGc...");
 ```
 
+__Decode with extended type__
+
+```ts
+const decodedToken = jwtDecoder<JWTDecoded & {
+  // Extra attributes here
+}>("eyJhbGc...");
+```
+
 ## Kinde documentation
 
 [Kinde Documentation](https://kinde.com/docs/) - Explore the Kinde docs