Update README for Q3

[CDDelta]

Bug, feature request, or proposal:

Proposal

What is the expected behavior?

README is up to date

What is the current behavior?

README is out of date

What are the steps to reproduce?

Providing a StackBlitz reproduction is the best way to share your issue.

StackBlitz starter: https://goo.gl/wwnhMV

What is the use-case or motivation for changing an existing behavior?

Would be nice to know material team priorities.

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

Is there anything else we should know?

[angular-automatic-lock-bot]

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