unsafe: add docs for SliceData, String, and StringData
Updates #53003.
Change-Id: I076d1eb4bd0580002ad8008f3ca213c5edc951ee
Reviewed-on: https://go-review.googlesource.com/c/go/+/427095
Run-TryBot: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: David Chase <drchase@google.com> Reviewed-by: Rob Pike <r@golang.org> Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com> Reviewed-by: Ian Lance Taylor <iant@google.com>