Extract data elements details from html content
Examples
if (FALSE) { # \dontrun{
library(grabr)
s <- pano_session("<my-pano-user>", "<my-password>")
url <- "https://pepfar-panorama.org/forms/downloads"
cont <- pano_content(page_url = url, session = s)
elts <- pano_elements(page_html = cont, page_url = url)
} # }