Point picker has a non ideal cursor shape

The tool [`pick_point_from_image`](https://github.com/shippp/hipp/blob/a7506adaf5667013385ae6db8595579d7e85f657/src/hipp/tools.py#L80) displays the cursor with a hand shape (at least on my version).
This is not ideal for accurately picking the fiducial marker. Maybe this can be improved.
