How to Add Up/Down Arrows to HTML Table That Can Be Sorted

[paulp575]

I am trying to add up/down arrows to an HTML table that can be sorted.

I found the W3Schools example of how to sort a table by clicking on the table headers - https://www.w3schools.com/howto/howto_js_sort_table.asp (second example "Sort Table by Clicking the Headers").

I'd like to add the up/down arrows to the table headers.