Edits to the new Next.js page

- Updated title
- Changed "NextJS" to "Next.js" to match their naming
- Added recommendation on folder structure
- Updated examples to match that folder structure
- Added typed hooks setup and usage
- Renamed `StoreType` to `AppStore`
- Updated store init to always use `if (!storeRef.current)`
- Updated section headers
- Added "RTKQ doesn't do SSR yet" callout

Author: markerikson

docs/tutorials/overview.md

@@ -31,7 +31,7 @@ The [**Redux Toolkit Quick Start tutorial**](./quick-start.mdx) briefly shows ho
 
 We also have a [**TypeScript Quick Start tutorial**](./typescript.md) that briefly shows how to set up and use TypeScript with Redux Toolkit and React-Redux.
 
-If you are using NextJS we have a tutorial specific to using Redux Toolkit with NextJS [**NextJS tutorial**](./nextjs.mdx).
+If you are using Next.js we have a tutorial specific to using Redux Toolkit with Next.js [**Next.js tutorial**](../usage/nextjs.mdx).
 
 ## Redux Essentials: A Real-World Example