Consider changing AXRoleDescription for landmark <header> from "banner" to "header"

[jasonkiss]

From ARIA issue #155

In HTML-AAM, UIA uses localized strings "header" and "footer" for both landmark and non-landmark instances of header and footer, differentiating between the two instances via LandmarkType.

In AX, the non-landmark instances are simply mapped to the AXGroup role with "group" as the localized string. The landmark instances of header and footer use "banner" and "footer" respectively. @cookiecrook, I'm assuming you're comfy with this, or do you want to follow suit and use "header" as the AXRoleDescription for the landmark instance of header?

[jasonkiss]

Both Chrome and Safari are the same in exposing landmark instance of header with "banner" localized string. Moving to v2.