Merge 5 release notes into RELEASE_NOTES.md

Change-Id: I7177215f838de4ed8a4fda9960a8f63627c3d9ee
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/1049138
Reviewed-by: Heather Miller <hcm@google.com>
6 files changed