Add extra_css to spec family
diff --git a/R/column_spec.R b/R/column_spec.R
index 55e01a1..a640a4d 100644
--- a/R/column_spec.R
+++ b/R/column_spec.R
@@ -23,6 +23,8 @@
 #' @param border_right A logical variable indicating whether there should be a
 #' border line on the right of the selected column. In HTML, you can also pass
 #' in a character string for the CSS of the border line
+#' @param extra_css Extra css text to be passed into the cells of the row. Note
+#' that it's not for the whole column but to each individual cells
 #'
 #' @examples x <- knitr::kable(head(mtcars), "html")
 #' column_spec(x, 1:2, width = "20em", bold = TRUE, italic = TRUE)
@@ -31,7 +33,8 @@
 column_spec <- function(kable_input, column,
                         width = NULL, bold = FALSE, italic = FALSE,
                         monospace = FALSE, color = NULL, background = NULL,
-                        border_left = FALSE, border_right = FALSE) {
+                        border_left = FALSE, border_right = FALSE,
+                        extra_css = NULL) {
   if (!is.numeric(column)) {
     stop("column must be numeric. ")
   }
@@ -44,7 +47,7 @@
     return(column_spec_html(kable_input, column, width,
                             bold, italic, monospace,
                             color, background,
-                            border_left, border_right))
+                            border_left, border_right, extra_css))
   }
   if (kable_format == "latex") {
     return(column_spec_latex(kable_input, column, width,
@@ -57,7 +60,7 @@
 column_spec_html <- function(kable_input, column, width,
                              bold, italic, monospace,
                              color, background,
-                             border_left, border_right) {
+                             border_left, border_right, extra_css) {
   kable_attrs <- attributes(kable_input)
   kable_xml <- read_kable_as_xml(kable_input)
   kable_tbody <- xml_tpart(kable_xml, "tbody")
@@ -118,6 +121,10 @@
         xml_attr(target_cell, "style") <- paste0(xml_attr(target_cell, "style"),
                                                  "border-right:", border_r_css, ";")
       }
+      if (!is.null(extra_css)) {
+        xml_attr(target_cell, "style") <- paste0(xml_attr(target_cell, "style"),
+                                                 extra_css)
+      }
     }
   }