Listing huge dirs

[kivimango]

Listing huge dirs with thousands of files are slow to read, and does not render: i think the ui is refreshed before the file list could be drawn into the ui.

Listing should be done on a separate bakcground/worker thread, or go async using tokio. I would flavor the worker thread solution, to keep the small footprint of the app, and not bloat the binary with tokio stuff.