doc: add release notes for changes to encoding/json package
The escaping of certain control characters has been changed.
The change is compliant with the JSON specification.
The JSON package never promised exactly how JSON formatted
and has historically changed its representation over time.
Change-Id: I8b23f503cfff86c460f642693b50dee24038fb0d
Reviewed-on: https://go-review.googlesource.com/c/go/+/548075
Run-TryBot: Joseph Tsai <joetsai@digital-static.net>
Auto-Submit: Joseph Tsai <joetsai@digital-static.net>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Robert Griesemer <gri@google.com>