Implement cropper.js

[flauc]

We need to implement cropper.js for our file-list and file-upload components.
It should be completely configurable and by default it shouldn't be displayed at all and both components should just work the way they currently do, however when options for the cropper are provided in that case before appending an image the cropper should be opened.

https://fengyuanchen.github.io/cropperjs/

Cropper.js is something that the implementer should add as an external dependency, just how we've implemented the JSON editor.

https://jaspero.github.io/web-components/docs/Editors/json-editor