[Enhancement] A11y improvements for Menu

[RasmusKjeldgaard]

• [x] I have written a good issue

Describe the enhancement

We should implement something like the actions menu pattern for our menu, to get proper support for keyboard interaction and proper announcing to screen readers: https://www.w3.org/WAI/ARIA/apg/patterns/menu-button/examples/menu-button-actions/

Describe the solution you'd like

• [ ] Correct role for the action button
• [ ] Correct role, tabindex etc. for the menu items
• [ ] Roving tabindex support or similar on keyboard interactions

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Checklist:

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Refinement

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