Update README.md

Updating README to include accessibility information

Author: MelSumner

README.md

@@ -12,6 +12,9 @@
 * Support for `keyup`, `keydown`, and `keypress`, as well as the modifier keys: `ctrl`, `alt`, `shift`, and `meta`.
 * Compatible with Ember 2.0+.
 
+## Accessibility Considerations
+In order to avoid adding keyboard shortcuts to your application that are already in use by assistive technology, please review the existing keyboard shortcuts and gestures available today: https://dequeuniversity.com/screenreaders/. 
+
 ## Installation
 
 `ember install ember-keyboard`