Handle complexities for footer/contentinfo landmark

[MelSumner]

The HTML5 footer element is not considered a contentinfo landmark when it is descendant of any of following elements:

• article

• aside

• main

• nav

• section

• To make this better for Ember applications, we should ensure that the contentinfo landmark is used appropriately. There may be some conversation/thought needed around how opinionated this addon wants to be regarding footer HTML element use.

[jenweber]

It seems that there are similar rules for banners https://www.w3.org/TR/wai-aria-practices/examples/landmarks/banner.html

[MelSumner]

@jenweber yes, you're correct. I might have it do some checking about what the parent element is and leave it at that.