Merge 4 release notes into RELEASE_NOTES.md

Change-Id: Id7afe676da39ba331c7a033b7a8c4a94c717d93e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/1329376
Bot-Commit: chrome-branch-day <chrome-branch-day@chops-service-accounts.iam.gserviceaccount.com>
5 files changed