Add columns fmt_fn, warning, and errors to ard_attributes output

[jtalboys]

What changes are proposed in this pull request?

• Add columns fmt_fn, warning, and errors to ard_attributes() output (Add warning and error columns to ard_attributes() output #327)

Provide more detail here as needed.

closes #327

Please let me know if there is anything else to change here. I'm not 100% sure I'm setting the fmt_fn column right? Also had a look at the docs for ard_attributes() to see if any changes were required but they only talk about the added attributes, don't mention the columns of the output.

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[ddsjoberg]

Thank you so much @jtalboys !! These look great! I just have one comment and the request below.

While reviewing I noticed that I had never added a check that the user-passed label argument is a named list. Can you also add a check like this?

  if (!is_empty(label)) {
    if (!is.list(label) || !is_named(label) || some(label, \(x) !is_string(x))) {
      cli::cli_abort(
        "The {.arg label} argument must be a named list with each element a string.",
        call = get_cli_abort_call()
      )
    }

[ddsjoberg]

This is wonderful, thank you @jtalboys !