The new function DT() used for chaining/piping drops `data.frame` rownames names

I noticed that the new function `DT()` drops  row names when applied to `data.frame`.

	df = mtcars[1:5, 1:2]
	df
			   mpg cyl
	Mazda RX4         21.0   6
	Mazda RX4 Wag     21.0   6
	Datsun 710        22.8   4
	Hornet 4 Drive    21.4   6
	Hornet Sportabout 18.7   8

	df |> 
	  DT(1:4, .SD)
	  
	   mpg cyl
	1 21.0   6
	2 21.0   6
	3 22.8   4
	4 21.4   6

