Enable definition of crop variants in EditingInterface.yaml

[typecat]

As an integrator, I can define crop variants for an image field, so that specific image sizes can be applied to the image field.

Acceptance criteria

• I can define crop variant in the EditingInterface.yaml
• The defined crop variants are applied to the corresponding image field in the same way as in TCA definition

Technical remarks

• Crop variants definition in the EditingInterface.yaml is resolved to a corresponding definition in the resulting TCA

[typecat]

Some conceptional work needs to be done here first. Also we need to consider whether we only want to support the configuration or also provide a default fluid rendering.

EDIT: Also, should the kickstarter support this?