## Description
This PR ensures that the default prettier config is used for examples
and templates.
This config is compatible with `prettier@3` as well (upgrading prettier
is bigger change that can be a future PR).
## Changes
- Updated `.prettierrc.json` in root with `"trailingComma": "es5"` (will
be needed upgrading to prettier@3)
- Added `examples/.prettierrc.json` with default config (this will
change every example)
- Added `packages/create-next-app/templates/.prettierrc.json` with
default config (this will change every template)
## Related
- Fixes#54402
- Closes#54409
## Changes
- Migrate class based `_document`s to functional documents
- Removed `_document.js` where default
- Removed `MyDocument.getInitialProps` where default
## Motivation
This removes some boilerplate and prepares examples for server components.
## Documentation / Examples
- [x] Make sure the linting passes by running `pnpm lint`
- [x] The examples guidelines are followed from [our contributing doc](https://github.com/vercel/next.js/blob/canary/contributing.md#adding-examples)
[ch2502]
- Added new import flow to every CMS example, using the deploy button, and removed `vercel.json`
- Replaced `dotenv` with the new env support in outdated examples
