message: docs: update release nots with blog post
  PR Close
diff: ### Release Highlights
  +To learn about the release highlights and our CLI-powered automated update workflow for your projects please check out the [v9.1 release announcement](https://blog.angular.io/version-9-1-of-angular-now-available-typescript-3-8-faster-builds-and-more-eb292f989428).
  +
  * TypeScript 3.8 update
  * ngcc improvements
  * performance optimizations
  