Add `modify_header(unhide_hidden)` argument?

I was working with a table where I needed to assign the names and I used `ends_with("_1")`, and it ended up unhiding a bunch of columns i didn't want to be shown.

Another option would be to include a new selectors `all_hidden_columns()`and `all_unhidden_columns()`.

Maybe all of the above, but I think scoping the hidden data for selecting may be overkill?