added header_separate function based on the suggestion in #541
diff --git a/man/header_separate.Rd b/man/header_separate.Rd
new file mode 100644
index 0000000..60a5d31
--- /dev/null
+++ b/man/header_separate.Rd
@@ -0,0 +1,21 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/header_separate.R
+\name{header_separate}
+\alias{header_separate}
+\title{Separate table headers and add additional header rows based on grouping}
+\usage{
+header_separate(kable_input, sep = "[^[:alnum:]]+")
+}
+\arguments{
+\item{kable_input}{Output of \code{knitr::kable()} with \code{format} specified}
+
+\item{sep}{A regular expression separator between groups. The default value
+is a regular expression that matches any sequence of non-alphanumeric values.}
+}
+\description{
+When you create a summary table for either model or basic
+summary stats in R, you usually end up having column names in the form of
+"a_mean", "a_sd", "b_mean" and "b_sd". This function streamlines the process
+of renaming these column names and adding extra header rows using
+\code{add_header_above}.
+}