Dropping file on first position under directory might put it in parent directory

[KoBeWi]

Godot version:
3.2.1

Issue description:

See that the line can be short and long, which might be confusing if you don't notice.

[dreamsComeTrue]

IMO, I think, when parent dir is selected as a target, it could be emphsized more clearly, by putting some dashed rect around it (or any other visual indicator), like: