* (feat) add a checkbox in `MainWindow` to enable cleaning input directories
after processing images.
* (feat) add `clean_up_input_dirs` flag attribute in `Decensor` class to
manage the cleanup operation.
* (feat) add `clean_input_directories()` method in `Decensor`
to remove `.png`, `.jpg`, and `.jpeg` files from input directories.
* (feat) add `do_post_jobs()` method being called after decensoring process is
completed.
* (feat) integrated logic to set `clean_up_input_dirs` via a signal emitted
from `MainWindow`.