add triangle to indicate drop down

[k-doering-NOAA]

Thanks @rklasky for suggesting this!

In visiting the FIT page again, one thing you might consider is adding a little triangle for those boxes that are actually pull-downs. It's kind of a standard GUI thing.

[k-doering-NOAA]

Here's an example: https://coastwatch.noaa.gov/cwn/index.html