Develop capability to copy images to and from a directory on the filesystem

## Overview

We are working on the ability to copy images between two registries while maintaining digest integrity
- https://github.com/containers/containerimage-py/issues/12

That effectively would serve as a python-native implementation of
```bash
# Copy from registry to registry
skopeo copy docker://$SRC_IMAGE docker://$DEST_IMAGE
```

This issue will focus on a similar capability, this time a python-native implementation of
```bash
# Copy from registry to directory
skopeo copy docker://$SRC_IMAGE dir:$DEST_DIR

# Copy from directory to registry
skopeo copy dir:$SRC_DIR docker://$DEST_IMAGE
```

## Acceptance

- [ ] It is possible to copy an image from a registry to a directory using `containerimage-py`
- [ ] It is possibly to copy an image from a directory to a registry using `containerimage-py`
- [ ] The usage of these new capabilities are documented
- [ ] Example scripts are written for these new capabilities
- [ ] There is unit test coverage for these new capabilities