This function tries to convert character vectors into integers. This function should not be called on page ranges.
Examples
jst_clean_page("2")
#> [1] 2
# anything that is not a digit gets removed
jst_clean_page("A2-")
#> [1] 2
# a weird format from the American Journal of Sociology is convered correctly
jst_clean_page("AJSv104p126")
#> [1] 126
# this is done by searching for "p", and if it is found, extracting the
# content after "p".