In a project with `"type": "module"` in `package.json` and a `compilerOptions.moduleResolution` of `Node16` or `NodeNext` in `tsconfig.json`, running `tsc` will yield errors like the following:

```
.next/types/app/[...not_found]/page.ts:1:40 - error TS2307: Cannot find module 'next/dist/lib/metadata/types/metadata-interface' or its corresponding type declarations.

1 import type { ResolvingMetadata } from 'next/dist/lib/metadata/types/metadata-interface';
                                         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

.next/types/app/layout.ts:2:24 - error TS2835: Relative import paths need explicit file extensions in EcmaScript imports when '--moduleResolution' is 'node16' or 'nodenext'. Did you mean '../../../app/layout.jsx'?

2 import * as entry from '../../../app/layout'
                         ~~~~~~~~~~~~~~~~~~~~~

.next/types/app/layout.ts:3:40 - error TS2307: Cannot find module 'next/dist/lib/metadata/types/metadata-interface' or its corresponding type declarations.

3 import type { ResolvingMetadata } from 'next/dist/lib/metadata/types/metadata-interface'
                                         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
```

Adding the extensions will make it work with these projects and still maintain backwards compatibility with other TypeScript / module configurations.