Improve Accordion implementation for Accessibility

[mertsincan]

Accordion codebase has been completely overhauled and is now closer to spec. In addition, some extra changes were made to the design based on user feedback.
https://www.w3.org/WAI/ARIA/apg/example-index/accordion/accordion#kbd_label
https://w3c.github.io/aria-practices/examples/accordion/accordion.html

Added Properties For Accordion:

• tabindex: Index of the element in tabbing order.
• selectOnFocus: When enabled, the focused tab is activated.

Added Properties For AccordionTab:

• headerStyle: Inline style of the tab header.
• headerClass: Style class of the tab header.
• headerProps: Uses to pass all properties of the HTMLDivElement to the tab header.
• headerActionProps: Uses to pass all properties of the HTMLAnchorElement to the focusable anchor element inside the tab header.
• contentStyle: Inline style of the tab content.
• contentClass: Style class of the tab content.
• contentProps: Uses to pass all properties of the HTMLDivElement to the tab content.