Paste images to file assets browser and/or editor

Great work on v3!

In v2 you could Cmd-V in the upload screen to paste files (typically screenshots). This was very useful when writing e.g. user manuals on the wiki. It would be great if this would return (either Cmd-V in the editor or in the file asset window).

A question is how the filename is determined. In v2 it would always be 'image.png' by default, and then you'd have to rename. A nicer UX would be a popup showing pasted thumbnails and then an input field to determine the file name.