Get the XML closing tag
Examples
check_empty_beautier_folder()
# my_tag
get_xml_closing_tag("<my_tag text=something></my_tag>")
#> [1] "my_tag"
# Will return NA
get_xml_closing_tag("<my_tag text=something/>")
#> [1] NA
get_xml_closing_tag("no_xml")
#> [1] NA
check_empty_beautier_folder()