Custom "special files" for App Router

[Charismara]

Goals

1. Providing an API to Devs that allow them to define custom "special files" (like layout.tsx) in the app router.

Non-Goals

No response

Background

Example use-case:

Creating a breadcrumb.tsx file on each route which gets joined and rendered in a specific slot in the root layout.

Or

Creating a sidebar.tsx on some routes to automatically create an entry within a sidebar component within the root layout.

Proposal

I have no idea how this could be implemented.

[Arinji2]

Not a fan of this, custom files with special meanings from codebase to codebase.. that will hurt