Make list-item component accessible for keyboard navigation

[aniri]

It should be possible to navigate between list items using the tab key.

Suggestions:

• add tabindex property - https://developer.mozilla.org/en-US/docs/Web/Accessibility/Keyboard-navigable_JavaScript_widgets#Using_tabindex
• user aria attributes - https://www.w3.org/TR/wai-aria-practices/

[danmana]

I can take this