Add drop-down list to body
add_dropdown_list(my_html, into = "", options, ...)html in a vector of strings; output from 'create_html'.
character string; unique identifier of a line in the html. Element id is highly recommended.
character vector; the options in the drop-down list. Each item must be unique.
Extra parameter that goes into a tag, e.g. In <div type = "xxx">, 'type = "xxx"' goes to ... .