Fix snap-in split window background color
Fix snap-in split window background color

The background color of the snap-in split window, which appears when a
tab of a tab group is dragged, had the same color as base background
(nord0). This has been changed to nord1 with a transparency of 60%.

GH-40

arcticicestudio/nord-visual-studio-code,arcticicestudio/nord-visual-studio-code