docs: fix missing auth.d.ts session types in server dir Nuxt 4 (#437)

Author: Eckhardt-D

README.md

@@ -156,6 +156,9 @@ const session = await requireUserSession(event)
 
 You can define the type for your user session by creating a type declaration file (for example, `auth.d.ts`) in your project to augment the `UserSession` type:
 
+> [!NOTE]
+> If you are using Nuxt >=4.0.0 or compatibility version 4 add the `auth.d.ts` file to the `shared` directory to get the correct types in server and client.
+
 ```ts
 // auth.d.ts
 declare module '#auth-utils' {