Draft: Adds RovingTabindexContainer component

What does this MR do and why?

Use component in markdown header with role toolbar

This reduces the number of tabstops required

Handles ArrowLeft & ArrowRight as per https://www.w3.org/TR/wai-aria-practices/examples/toolbar/toolbar.html

Related to Reduce the number of tabstops on the Markdown t... (#225542 - closed) & Issue tab stops could be better (#300965)

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