feat: allow styling based on whether a file is hidden

I often use the `-a` option because I want to see a full picture of my environment and not have things hidden from me, but I often do still wish there was some sort of visual distinction between regular files and hidden files in the list. I tried to add styling to that effect into my theme file, but unless I missed some crucial piece of documentation it looks like there is no way to target files in a theme based on their hidden-ness. I would like to have an option for that.