feature: html classes for heading wrapper

[Paul-Bob]

Description

Allow html option classes for heading field wrapper:

      field :user_information, as: :heading, html: -> {
        edit do
          wrapper do
            classes do
              record.something? ? "hidden" : ""
            end
          end
        end
      }

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works

[codeclimate]

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[github-actions]

This PR has been merged into main. The functionality will be available in the next release.

Please check the release guide for more information.