Feature Request: Support maintaining original aspect ratio with max dimension scaling

[smithereensarr]

Hi! 👋
I noticed that photo_manager library supports getting photos with automatic scaling while maintaining the original aspect ratio by specifying a maximum dimension. For example:

// photo_manager supports this
final thumbnailData = await asset.thumbnailDataWithOption(
  ThumbnailOption.ios(
    size: ThumbnailSize.square(maxDimension),
    resizeContentMode: ResizeContentMode.fit, // maintains aspect ratio
  ),
);

Currently, insta_assets_picker only supports fixed crop ratios (like 1:1, 4:5) which forces users to crop their images to specific aspect ratios.

Would it be possible to add this feature? Perhaps as an additional option in InstaAssetCropDelegate or a new configuration parameter?
Thanks for your great work on this library! 🙏