Render a help text the field

[alies-dev]

Nova fields have help text that can be specified by ->help($text) method. Both TextWithSlug and Slug don’t render this help text.

[elliottregan]

attributes would be nice, too. I'm looking to make the slug non-editable, so users can't mangle the slug with spaces, and Slug::make('slug')->attributes(['readonly']) would allow me to do that.