docs: improve file tree

[devjiwonchoi]

The file tree can be improved and share the same convention:

• Use the txt file extension.
• One tab indented.
• Use file tree with root . and trailing slash for folders.

x-ref: https://tree.nathanfriend.io

[devjiwonchoi]

• docs: improve file tree #77889 👈 (View in Graphite)
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[eps1lon]

Is this the only page we display a file tree in docs? Should strive for consistency here if possible.

[devjiwonchoi]

Tried to cover existing file trees and apply same format.

[eps1lon]

Does that work with the current release of Geist font or do we need to wait for vercel/geist-font#158?

[devjiwonchoi]

Does that work with the current release of Geist font or do we need to wait for vercel/geist-font#158?

The change is based on the existing code frame format of the extension txt. I don't expect it to be affected since it doesn't at the moment.

x-ref: https://nextjs.org/docs/app/building-your-application/configuring/mdx#using-file-based-routing
(For future readers, the content in this link may differ)