Adds an image to the page with an optional caption.
Improved approach for retina screens
Uses two versions of the image, one for standard screens and the other for retina screens.
We specify a folder path for both small and large images which is defined in the macro as
largeSrc. The filename is expected to be the same for both.
If the image is decorative and does not convey important information, do not add an alt tag. This will then be hidden from screen reader users.
Specifies a single image that would appear blurry on retina displays.
This continues to use the original macro property
url for the image path.