Pass id or name of current sheet in callback function in importSheets

[aatanasijevic]

It would be good to have the current sheet id/name to the $callback arguments in the importSheets method. It can be useful for data validation messages, especially when you can have the same field names in different sheets. Something like:
if ($callback) { if ($result = $callback($sheet->getName(), empty($headers) ? $row : array_combine($headers, $row))) { $collection[] = $result; }