pass through aria- props on Button component
as well as data- and any other dashed props

typescript won't alert us to a dashed prop being passed to a component
where it isn't accepted, so it's safest to pass them through wholesale:
https://github.com/microsoft/TypeScript/issues/32447

partial fix to: https://github.com/mdn/yari/issues/8015

* fix: improve aria labels on mobile sidebar button

fixes: https://github.com/mdn/yari/issues/8015

* dashedProps -> passthroughAttrs