Enumerate the problems this solves not addressed by ember-a11y

From the [associated blog post](https://engineering.linkedin.com/blog/2018/10/making-ember-applications--ui-transitions-screen-reader-friendly):

> Initially we wanted to use the existing ember-a11y addon to make the dynamic UI transitions screen reading software compatible. However after initial integration, we discovered that this addon could not be used as is and needed a couple of prerequisites to be addressed.

Can you make this concrete and enumerate the issues in the README or alternatively file bugs upstream?
- So that they can possibly be addressed in ember-a11y. (This reads as FUD or, ironically, NIH without it.)
- So that users can make informed decisions.

Ember tries to have a single canonical solution to problems, this is a step away from that pattern.

Read the associated blog post and investigate the ember-a11y prerequisites described there. Compare those limitations with this project's behavior, then enumerate concrete issues in the README or file corresponding bugs upstream. Done means users can understand what ember-a11y does not address and make an informed choice.

Written by the indexing model from the issue text.