Add functionality for the duplicate scanner. This uses the
previously-implemented code to derive SHA-256-based hashes and detect
duplicates before deleting them. Arguments are provided for a dry-run
mode and directory selection.
Add an argument which allows the user to specify which directory should
be scanned for duplicates, rather than hard-code the directory into the
script. This makes the script portable and easier-to-use.
Add a dry-run argument so the user can have the script detect duplicates
without deleting them. This is useful for informing the user of which
files would be deleted, should they run the script, normally.
