horizontal/vertical line image annotation

Hi,

I wanted to add an Icon as an annotation to a horizontal/vertical line, and I saw that the only solution is to use an Image or a SizedPicture object, for which we have an example in the readme. I realised that there is also no parameter to change the position of the annotation in the y axis, which would be nice to have.

I saw the discussion when this line annotation feature was added and I think it would be best if this was generalised using Widgets instead of having separate parameters for Images or SizedPictures. Maybe this new annotation feature with widgets could be even more generalised and added to other objects such as RangeAnnotations, etc.

Thank you.

Start with the README's Image/SizedPicture line-annotation example and the existing horizontal/vertical line annotation API. Review the requested y-axis positioning and widget-based design, including whether related annotations such as RangeAnnotations belong in scope; done means the supported behavior and scope are clearly defined and validated.

Written by the indexing model from the issue text.