* Explicitly download files to _files (you'll be prompted to update the
storage format the first time you run wayslack)
* Add delete_old_files option, which can automatically delete files
from Slack that are older than a particular age. For example:
delete_old_files: 60 days
Will delete files from Slack that are more than 60 days old. This is
probably only useful for users of the free tier who are limited to
5gb of storage.
As you'd hopefully expect, only files which exist in the local wayslack
archive will be deleted.