I found the documentation for Pinner itself to contain too little information.
Rewrite it to give a summary and redirect to the relevant methods.
Also reformat the ragged comment for Pin.
Change-Id: I9c786817f43dfc9c72178127c141c35dae221104
Reviewed-on: https://go-review.googlesource.com/c/go/+/528855 Reviewed-by: Ian Lance Taylor <iant@google.com> Reviewed-by: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>