Help option for headline fields#139

I would love to have a field property “help” for headline fields which should be placed below the headline.
(https://getkirby.com/docs/reference/panel/fields/headline#field-properties)

It would allow to describe the following block and would save the usage of another field. Currently I use an additional info field for description which looks not perfect because of to much margin and different style as well.

Just a small improvement, but it would be very helpful for my blueprints :-)

Thanks for implementing this idea :)