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)
