[Dropdown] Accessibility requirements

[aweell]

WAI-ARIA Authoring practices 1.2

https://www.w3.org/TR/wai-aria-practices-1.2/#menubutton

WCAG 2.2

https://www.w3.org/TR/WCAG22/#content-on-hover-or-focus
https://www.w3.org/TR/WCAG22/#on-input

[aweell]

Closed via #248