Implement reveal mode for OnyxHeadline

[larsrickert]

Why?

The existing OnyxHeadline component should support a reveal mode that can be used to reveal content (similar to the accordion).

Open questions / TODOs

• should the revealed content be part of the headline (e.g. a slot) or be placed by the project?
  • @JoCa96: For now use the slot to keep the implementation simple

Depends on

• Implement OnyxAccordion component #2140

Design

Figma

Acceptance criteria

• an optional reveal mode is supported by the OnyxHeadline
• the API is the same as for the OnyxAccordion / OnyxAccordionItem
• keyboard is supported

Implementation details

<-- Add technical details / implementation proposals if necessary, e.g.:

• API proposal
• relevant web APIs
• learnings from other implementations
• code snippets
  -->

Reference implementations

OnyxAccordion

Applicable ARIA Pattern

Accordion pattern

Definition of Done

• The following component requirements are implemented:

  • skeleton
  • density
  • example usage added to apps/demo-app/src/views/HomeView.vue

• Should be covered by tests:

  • functional tests (Playwright or unit test)
  • visual tests (Playwright screenshots)

• Make sure, that

  • follow-up tickets were created if necessary
  • updated version + documentation is deployed
  • Storybook can show the feature
  • Storybook code snippet of new/changed examples are checked that they are generated correctly
  • Namings are aligned with Figma

Approval

Storybook
Documentation

• Checked and approved by
  • designer
  • dev