nplowman → created an issue.
I just opened a pull request (#4) with one possible solution for adding keyboard controls, for consideration.
It adds left, right, up, and down buttons for moving the crop selection and "smaller" and "bigger" buttons for resizing the crop selection area.
Being able to set the crop area using keyboard is also very important for accessibility.
Taking a look at this module though, it looks like it makes use of a third party library (cropper.js) for the actual crop functionality.
So making this module keyboard-accessible might require forking or replacing this library entirely.
This is something I need to solve for on a current project, so will post a follow-up if I find a good solution.