Create a 'loading' state for preview of cropped area.

[brizental]

Sometimes when the cropped area is too big it takes to long to show the preview of the crop. Better to add a loading gif or something for the user not to think that the interface is frozen.

Also, the preview freezes the whole interface when the image is too big. That's a problem.

[brizental]

IDEA

For optimizing the preview we could just not crop the area for previewing. Insted put the whole image in the preview area but only show the cropped area.

For this to make a bit more sense, we can just take a look at cropper.js, that's where I got the idea: https://fengyuanchen.github.io/cropperjs/