Docker-export

Added

- `get_export_filename(image, platform)` for an fs-safe filename

Changed

- `fs_name` now includes image reference and is filesystem safe for all OS.
- Default export filename now includes platform as well.

Changed

- Default-variant-safe `Platform` comparison (fixes linux/arm64/v8 not == linux/arm64)

Added

- `Image.exists()`/`image_exists()` function to check registry for an image+platform
- `Image.get_digest()`/`get_image_digest()` function to retrieve unique image+platform digest
- Proper type hints

Changed

- Fixed Python 3.8 and 3.9 usage (was using 3.10+ specific feature)

Removed

- Support for python 3.6 and 3.7 (both EOL)