added spec_image, spec_hist, spec_boxplot and fixed some cran comments
diff --git a/man/column_spec.Rd b/man/column_spec.Rd
index aeff8ec..8d19fc7 100644
--- a/man/column_spec.Rd
+++ b/man/column_spec.Rd
@@ -26,7 +26,8 @@
   link = NULL,
   new_tab = TRUE,
   tooltip = NULL,
-  popover = NULL
+  popover = NULL,
+  image = NULL
 )
 }
 \arguments{
@@ -99,6 +100,8 @@
 to build a popover is through \code{spec_popover()}. If you only provide a text
 string, it will be used as content. Note that You have to enable this
 bootstrap module manually. Read the package vignette to see how.}
+
+\item{image}{Vector of image paths.}
 }
 \description{
 This function allows users to select a column and then specify