Add support for managing `node_modules/.ignored` folders separately in npkill

[sauryagur]

Is your feature request related to a problem? Please describe.
When using pnpm after having previously installed packages with npm, the old node_modules directory often gets moved to .ignored. Currently, npkill doesn’t display .ignored folders in a clear or separate way, which makes it harder to identify and manage them.

Describe the solution you'd like
I’d like npkill to show .ignored directories grouped under a collapsible tree (or similar structure) so they’re visually distinct from regular node_modules. Additionally, I’d like an option to delete .ignored separately, (.ignored will be automatically removed if the parent node_modules folder is deleted).

Describe alternatives you've considered
Manually navigating to each .ignored directory and deleting it, which is time-consuming and less convenient.

Additional context
This would be especially useful when switching between package managers (npm → pnpm) to clean up leftover directories without confusion.