addPasteFilesListener function
Registers a listener for paste events containing file data.
On web, listens to the browser paste event and extracts file items
from the clipboard data. On other platforms, this is a no-op.
The callback is invoked only when the paste contains file items.
Implementation
void addPasteFilesListener(PasteFilesCallback callback) =>
impl.addPasteFilesListener(callback);