Change READMEs of created turborepos (reflect appDir) (#5583)
Hi everyone, thanks for the continued work on turbo!
### Description
I created a new turborepo today with `pnpm dlx create-turbo@latest` and
noticed that the READMEs of both apps still reflect the `pages`
directory, but the apps themselves use the `app` directory.
So, I looked through all created packages and changed the necessary
parts in the READMEs if the created next.js app uses the `app`
directory.
### Testing Instructions
No big changes, just READMEs.
