Merge 8 release notes into RELEASE_NOTES.md

Change-Id: Ifdabdbb03f53890e0f8f7c6fcd9955bd9c32f99d
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/1086478
Reviewed-by: Eric Boren <borenet@google.com>
9 files changed