Improve api template

[Tim-Zj]

What?

• Updated .env.example file to include additional environment variables for API configuration and miscellaneous settings.
• Added route.js to configure API routes using the App Router, including handling of GET, POST, PUT, and DELETE methods.

Why?

• To provide a more comprehensive example for developers, making it easier to configure and manage environment variables.
• To enhance the API routes configuration by setting body size limits and enabling CORS with specific HTTP methods, improving security and flexibility.
• To align with the App Router approach as recommended by the Next.js documentation.

How?

• Modified .env.example to include API_BASE_URL, API_VERSION, NODE_ENV, and PORT.
• Added route.js in packages/create-next-app/templates/api/js/app/api/ to handle API routes with proper HTTP methods and response configurations.

Closes NEXT
Fixes #68256

[ijjk]

Allow CI Workflow Run

• approve CI run for commit: 5f3888f

Note: this should only be enabled once the PR is ready to go and can only be enabled by a maintainer

[devjiwonchoi]

Hi @Tim-Zj! Could you push to #68130, not on another PR? Thank you!! 😄

[Tim-Zj]

@devjiwonchoi Sure, got it!

[Tim-Zj]

@devjiwonchoi I have merged the changes into the feat-headless-api branch,Thank you!