New component: Modal

[mrosvik]

Related information and insight

• https://design.entur.org/komponenter/layout-og-flater/modal
• https://aksel.nav.no/komponenter/core/modal
• https://carbondesignsystem.com/components/modal/code/
• https://designsystem.dk/komponenter/modal/

Modal specification

The Modal Component should be used to display content in a overlaying window of the current page or screen. It provides a focused and contextual interaction for users without navigating away from the main content.

Requirements

• Should support various types of content, including text, images, form-elements, buttons, link, lists, etc.
• Should support keyboard navigation, allowing users to interact using the keyboard alone.
• Should support scrolling within the modal if the content exceeds the viewport's height.
• Should support different languages.
• Should be responsive and adapt to different screen sizes, ensuring optimal usability on desktops, tablets, and mobile devices.
• Should follow accessibility standards, including proper semantic markup, correct use of ARIA attributes and keyboard accessibility. It should provide text alternatives for the icons.

Underlying content:

• Should create a visually distinct overlay to darken the underlying content.
• Should prevent interaction with the underlying content while the modal is active.
• Clicking outside the modal window or on the overlay should close the modal.

To be considered:

• We should consider if the modal should come in different sizes with different spacing.
• We should consider if the modal should support brand-colors.
• We should consider if the modal shall provide a close button in top or a button in bottom to dismiss the modal to allow users to exit the overlay.

### Tasks
- [ ] https://github.com/digdir/designsystem/issues/585
- [ ] https://github.com/digdir/designsystem/issues/586
- [ ] https://github.com/digdir/designsystem/issues/587
- [x] Modal: WCAG-Test

[mrosvik]

The Modal component is ready for use: https://storybook.designsystemet.no/?path=/docs/felles-modal--docs