Attempting to preview a large or nested folder can take a long time

[conquillacarl]

I am worried that when previewing large or nested folders the app may crash. After some time attempting to fetch the data the process can be interrupted successfully, but I think it would be a lot more efficient to be able to manually interrupt quickly.

This would prevent quicklook from locking up when trying to work quickly, when accidentally trying to preview a large folder (especially if you didn't know it was a big folder)

[plant-life]

You can take a look at this. Related to #23