And also insert new paragraphs between GOOS and GOARCH listings
for better readability.

Fixes #28142
Fixes #26513

Change-Id: Ie92e98dbfd924e80032a12afbfa02f30e3a6f916
Reviewed-on: https://go-review.googlesource.com/c/go/+/189578Reviewed-by: Andrew Bonventre <andybons@golang.org>