v1.6.2 - mime(-type) it all the way

This release ensures that all Willow ImageFile subclasses define a mime_type attribute.

What's Changed

• Ensure SVG files are given a mime type by @RealOrangeOne in #129

New Contributors

• @RealOrangeOne made their first contribution in #129

Full Changelog: v1.6.1...v1.6.2