docs: 📚 improve a11y docs

[karlbaumhauer]

Description

In order to provide more detailed information about a11y requirements, limitations and important things we left open to provide more flexibility, we need to add a separate a11y-page to each components docs (as audi does).

Where to put the documentation

Storybook/Figma

DoR

• Item has business value
• Item has been estimated by the team
• Item is clear and well-defined
• Item dependencies have been identified

DoD

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

[yoezlem]

Since we will be receiving an a11y audit for all our components, I would like to temporarily block the ticket. After the audit, the ticket can be reopened.