Update L.DistortableImage.Edit.js function syntax to ES6 (#724)
Update L.DistortableImage.Edit.js function syntax to ES6 (#724)

Co-authored-by: Yoyogrego <c3ebddc5315b4837e8fbdd46d75c1a4a05b9f0d9@users.noreply.github.com>
publiclab/Leaflet.DistortableImage,publiclab/Leaflet.DistortableImage