[Date-picker] Accessibility requirements

**WAI-ARIA authoring practices 1.2:**
https://www.w3.org/TR/wai-aria-practices-1.2/#dialog_modal

**WAI-ARIA authoring practices date picker design pattern:**
https://www.w3.org/TR/wai-aria-practices/examples/dialog-modal/datepicker-dialog.html

**WCAG 2.2**
https://www.w3.org/WAI/WCAG22/Understanding/focus-visible