Add Princeton cropping tool to Image Tools

[triplingual]

https://mcgrawcenter.github.io/croppingtool/

This tool is intended to be used in course assignments that take advantage of IIIF-enabled digital image collections. Submit a manifest URL to build a gallery of thumbnails. Select a thumbnail to open that image in the right-hand window. Enable the cropping tool to extract details for use in discussion board posts or other course assignments.

This tool was developed at the McGraw Center for Teaching and Learning, Princeton University.