Gracefully handle non-writeable directory by using a default fallback path #500
Description
When extracting files or creating a new archive, Keka seems to just fail if the current directory is not writable by the user. Using a recent beta version (the one with ACE 2.x support), the app actually just crashed. (I included a crash log from that in the upload for the other ticket, about that beta).
I would suggest that what it should really do is save out to a pre-defined location, ~/Desktop/ by default, but configurable as a preferences option. Some apps that do this sort of fallback saving use ~/Downloads/, and others use ~/Documents/ or ~/Documents/App_name_here/ or whatever, and people may want to adjust Keka's fallback path to match whatever they're used to their other tools doing, and/or to mesh into some other workflow like a directory-watching app, or whatever. User choice is generally a good thing, while the user's desktop is a pretty typical default location for things, both in Mac and in Windows.
Ideally, Keka would report that it has done this and why, e.g. "Filename(s) saved to /The/Fallback/Path/ because /The/Original/Directory/ was not writable."