Action labels of the Actionbar component aren't HTML input of any kind and thus are not recognisable by screen readers.

• Similar Vaadin component com.vaadin.client.ui.VMenuBar doesn't seem to provide any WAI-ARIA support.
• It would be hard to come up with any kind of link types here since that's not how the actions work in admin central.
• Logical solution - investigate whether the reader devices would be satisfied if the actions were exposed as <input > elements (e.g. buttons).
• We could even have duplicate controls in there and the buttons hidden with CSS (e.g. see com.vaadin.client.ui.aria.AriaHelper#setVisibleForAssistiveDevicesOnly).