doc: add skeleton module documentation with headings
doc: add skeleton module documentation with headings

Sections will be filled in with individual CLs before Go 1.14.

NOTE: This document is currently in Markdown for ease of writing /
reviewing. Before Go 1.14, we will either ensure that x/website
can render Markdown (flavor TBD) or check in a rendered HTML file that
can be displayed directly.

Updates #33637

Change-Id: Icd43fa2bdb7d256b28a56b93214b70343f43492e
Reviewed-on: https://go-review.googlesource.com/c/go/+/202081
Reviewed-by: Bryan C. Mills <1c8aad60184261ccede67f5c63a0d2a3bf3c9ff4@google.com>

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