updates documentation

#' @param position position adjustment, either as a string, or the result of a

#' call to a position adjustment function.

#' @param geom one of text, label or richtext.

#' @param parse logical. IF TRUE (default), the labels will be parsed into expression.

#' @param parse logical or a parse function. IF TRUE (default), the labels will

#' be parsed into expression.

#' @param ... others passing to \code{ggplot2::geom_<geom>()}.

#' @return a gg layer object.

#' @rdname geom_magic_text

\item{geom}{one of text, label or richtext.}

\item{parse}{logical. IF TRUE (default), the labels will be parsed into expression.}

\item{parse}{logical or a parse function. IF TRUE (default), the labels will

be parsed into expression.}

\item{...}{others passing to \code{ggplot2::geom_<geom>()}.}

}