Add support for ariaRole property

[jelhan]

This adds support for ariaRole property:

• If it's value is a static string it's converted to a tagless component.

  export default Component.extend({
    ariaRole: 'button',
  });

  is converted to

  <div role="button"></div>

• If it's value is dynamic (most likely a computed property) the component is skipped. I expect this to be a rare edge case. So not doing the additional work to do it, might be okay.

This is kind of conflicting with #44. If support for native classes lands before, support for ariaRole in native classes needs to be added here. If this is merged before #44, support for ariaRole has to be added there. I don't care about the order.

Closes #49

[jelhan]

Sorry, too late, too tired. HTML attribute should not be applied to the created element and the ariaRole property be removed from the object.

@simonihmig Vielen Dank für den schnellen Review und das wachsame Auge!

[simonihmig]

Looks good! 👍

[Turbo87]

thanks for implementing this @jelhan! I've rebased this on top of #43 and will merge once it's green :)