expose existing image properties to scripting api

Expose the existing image properties to the interactive scripting api.

[#57828832]

This only exposes the _existing_ image properties in the md2d engine. It does not add new properties that may be of interest (e.g. visibility). Because image properties are treated differently that other scriptable elements (shapes, textboxes), adding and controlling other properties would require more extensive changes to the md2d engine and renderer.