doc: add sections for modules, packages, versions to module reference

Updates #33637

Change-Id: I3a0d05551d5a680febf742b912a5a6e5af753a6e
Reviewed-on: https://go-review.googlesource.com/c/go/+/206617


Run-TryBot: Jay Conrod <jayconrod@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Tyler Bui-Palsulich <tbp@google.com>