Allow setting padding for crop area

[coproductions]

Is your feature request related to a problem? Please describe.
When restrictPosition is set to false, it would be great if there was a way to add some padding to the sides/height of the crop area.
Currently when the image already has the correct aspect ratio or similar it fills out the entire crop area horizontally.

Describe the solution you'd like
It would be great to allow for there always to be a certain amount of grey border around the image in the crop area, to make it clear that they can zoom in both directions.

[ValentinH]

Thanks for using the issue template!
This issue might help you: #502

[coproductions]

Yes that helped. thanks