Thumbnail structure does not comply with W3 standards

[aykutkardas]

W3 standards do not allow a button to contain a div. However, in this package, thumbnail images have a div container and are contained within a button element.

Current Version: "react-image-gallery": "^1.0.8"

[aykutkardas]

Maybe it will be sufficient to replace the divs in the button with span.