document return value (amends c84816)

git-svn-id: https://svn.r-project.org/R/trunk@86479 00db46b3-68df-0310-9c12-caf00c1e9a41

Author: smeyer

src/library/graphics/man/grid.Rd

@@ -1,6 +1,6 @@
 % File src/library/graphics/man/grid.Rd
 % Part of the R package, https://www.R-project.org
-% Copyright 1995-2023 R Core Team
+% Copyright 1995-2024 R Core Team
 % Distributed under GPL 2 or later
 
 \name{grid}
@@ -28,6 +28,10 @@ grid(nx = NULL, ny = nx, col = "lightgray", lty = "dotted",
       FALSE} in that case gives \emph{non equidistant} tick aligned
     grid lines.}
 }
+\value{
+  A list of the x (\code{"atx"}) and y (\code{"aty"}) coordinates at
+  which the grid lines were drawn is returned invisibly.
+}
 \note{
   If more fine tuning is required, use \code{\link{abline}(h = ., v = .)}
   directly.