When a playlist is being played by Whirligig, and its UI is not opened, and files are drag and dropped, those files should still get added to the playlist, to the end.
if you drag and drop one file, it doesn't get added to the playlist, it gets played back immediately. instead, it should get added to the end of the playlist.
if you drag and drop multiple files, the first one gets played back immediately. instead, all of them should get added to the end of the playlist.
When a playlist is being played by Whirligig, and its UI is not opened, and files are drag and dropped, those files should still get added to the playlist, to the end.