add support for webp and maybe web image URLs

[OBrink]

Issue from @egonw posted here

"Allowing people to drag-n-drop images from articles, like https://www.nature.com/articles/s41586-022-04828-5/figures/1, which often are .webp format nowadays:"

[OBrink]

My problem right now is that the input fields don't accept multiple input types. When I define an input field as "type=file", then it won't accept a link. Maybe I could add the feature that the DECIMER logo becomes a text input field which triggers the processing of a given link, but I don't really think that that's an elegant solution