Opening file in new tab / drag and drop to system apps.

[ciembor]

Drag and drop was the way how some users used it in Mintty.

[ciembor]

Waiting for confirmation: mintty/mintty#1363 (comment)

[mintty]

I've now updated mintty to support drag-and-drop from the new 4bit URL format.
However, as noted in the mintty issue, it would be nice if it also works from the "Download Scheme" button and the ".minttyrc" button.