[Accessibility] Screen reader doesn't announce chip removal when a chip is removed via keyboard

[opozo]

Bug, feature request, or proposal:

When a chip [1] is removed via keyboard, screen reader doesn't announce it
[1] https://material.angular.io/components/chips/overview

What is the expected behavior?

When a chip is removed via keyboard, screen reader should announce chip removal.

What is the current behavior?

Screen reader doesn't announce chip removal when a chip is removed via keyboard.

Which versions of Angular, Material, OS, TypeScript, browsers are affected?

@angular/material: 6.3.0

[zarend]

Action item here is to update examples to announce when chip is removed using LiveAnnouncer. Also to update a11y documentation.