feat[dev]: ✨ implement A11y improvements to sd-headline

[yoezlem]

Description

This task describes the Storybook implementation for the sd-headline component as part of the A11y improvements outlined in Epic #1465.

A11y improvements for sd-headline can be found here: sd-headline Notes.

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Comment

The examples under "sizes" do the exact opposite of what the style description says. The paragraphs look like headings but aren't. You should clarify the description "Used as a crucial element for displaying content hierarchy and to enhance accessibility.". How’s it crucial and how does it enhance accessibility?

Open Questions

• Question1
• Question2

DoR

• Item has been estimated by the team
• Item dependencies have been identified and documented

DoD

• Documentation has been created/updated (if applicable)
• Migration Guide has been created/updated (if applicable)
• Relevant E2E tests (Features, A11y, Bug fixes) are created/updated
• Relevant stories (Features, A11y) are created/updated
• Implementation works successfully on feature branch