Support pasting from clipboard into file and image inputs

[JoCa96]

It was a question that came up in regard to CoreUI. We don't support it there, but I think it would be a neat idea to support pasting from the clipboard (when the input is focused). This would be quite simple to implement as both APIs support MIME types to identify content:

• https://developer.mozilla.org/en-US/docs/Web/API/Clipboard/read#parameters
• https://developer.mozilla.org/en-US/docs/Web/HTML/Element/input/file#accept

One step more might be to dynamically show an paste action button with the input when compatible content is detected.