@Alanscut Wow! Great work here. Can I ask you for two more changes?

1. Add/amend the README.md file showing how to add images with hyperlinks
2. Add an integration test that creates a new workbook containing an image with hyperlink and confirming that when the file is read back, it is as expected. spec/integration/workbook/images.spec.js has examples of how this is done

@guyonroche Thanks your review! Have added the testcase and update README file as you instructed.