chore: Refactor active-class-name example (#40670)

## Changes

- Migrated missing file to typescript

## 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/examples/adding-examples.md)

Author: HaNdTriX