No way for screen reader to read minValue,MaxValue,CurrentValue

## I'm submitting a...

[ ] Bug report  

[ ] Feature request

## Current behavior

## Expected behavior

## Minimal reproduction of the problem with instructions

## Environment

Library version: X.Y.Z

Angular version: X.Y.Z


Browser:

- [ ] Chrome (desktop) version XX

Start by inspecting the Angular star-rating component and reproducing its behavior with a screen reader. Determine how minValue, MaxValue, and CurrentValue are currently exposed, then verify that all three values can be read by the screen reader without changing the component's intended rating behavior.

Written by the indexing model from the issue text.