doc/go1.18: add Clone doc
doc/go1.18: add Clone doc

For #47694

Change-Id: I3b135f6ff199d7a9746726b131fbe7dd97a8e95e
Reviewed-on: https://go-review.googlesource.com/c/go/+/364254
Reviewed-by: Dmitri Shuralyov <d181b7fea0ec87c86ba5a890ab716db52498e3ba@golang.org>
Trust: Heschi Kreinick <e89ab2b172855aa0ad01c40c4d8a3535a61ac68a@google.com>

CAFxX/go,cloudflare/go,nawawi/go,golang/go,golang/go,cloudflare/go,golang/go,CAFxX/go,CAFxX/go,nawawi/go,CAFxX/go,CAFxX/go,cloudflare/go,cloudflare/go,cloudflare/go,nawawi/go,CAFxX/go,nawawi/go,cloudflare/go,cloudflare/go,CAFxX/go,CAFxX/go,nawawi/go,cloudflare/go,nawawi/go,nawawi/go,golang/go,golang/go,golang/go,golang/go,golang/go,nawawi/go