#' Embed local images using base64
#'
#' @keywords internal
#' @param html_in path to input html file
#' @param html_out path to output html file
#' @return 
embed_images <- function(html_in, html_out){
  html <- paste(readLines(html_in), collapse = "\n")
  html <- markdown:::.b64EncodeImages(html)
  writeLines(html, html_out)
}