internal/https: document
internal/https: document

For golang/go#49191.

Change-Id: I1fe2fc3fff2ba9add532b9c7d447f27ac6cfc54c
Reviewed-on: https://go-review.googlesource.com/c/build/+/359234
Trust: Heschi Kreinick <e89ab2b172855aa0ad01c40c4d8a3535a61ac68a@google.com>
Run-TryBot: Heschi Kreinick <e89ab2b172855aa0ad01c40c4d8a3535a61ac68a@google.com>
TryBot-Result: Go Bot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Alexander Rakoczy <60c6d277a8bd81de7fdde19201bf9c58a3df08f4@golang.org>
Reviewed-by: Carlos Amedee <ab5e2bca84933118bbc9d48ffaccce3bac4eeb64@golang.org>

golang/build,golang/build,golang/build,golang/build