Add documentation about r to gsDesign()

[nanxstats]

We should add details about r to the gsDesign() function documentation.

From

gsDesign/tests/gsDesign_independent_code.R

Lines 814 to 816 in 0f9b6a9

	#' @details
	#' Jennison and Turnbull (p 350) claim accuracy of \code{10E-6} with \code{r=16}.
	#' The numerical integration grid spreads out at the tail to enable accurate tail probability calcuations.

:

#' @details
#' Jennison and Turnbull (p 350) claim accuracy of \code{10E-6} with \code{r=16}.
#' The numerical integration grid spreads out at the tail to enable accurate tail probability calculations.