Existing documentation is a bit sparse, and more importantly focuses
almost entirely on the old pre-1.18 format, with the new format as an
afterthought. Since the new format is the primary format, make it more
prominent.
Updates #68592.
Change-Id: I108ecde1b33650b4812fa5d278b08cb9197f6329
Reviewed-on: https://go-review.googlesource.com/c/go/+/601456
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Cherry Mui <cherryyz@google.com>
Auto-Submit: Michael Pratt <mpratt@google.com>