Merge 3 release notes into RELEASE_NOTES.md

Change-Id: I55f67383af98d9e1c55b65b97fc81f8b052e74b2
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/864604
Reviewed-by: Heather Miller <hcm@google.com>
4 files changed