ImageSize: imageSize function fails for SVGs without width/height attributes

[ksesong]

When using .svg files that do not have an explicit width and height attribute, but a defined viewBox, the imageSize function from Text.Pandoc.ImageSize fails with the following error: [WARNING] Could not determine image size for './test-5.svg': could not determine SVG size.

For example, this image leads to this error. It was created using Adobe Illustrator's "Export for Screens..." function, so this is a relatively frequent situation.