sysutils/helm-docs: New port

A tool that auto-generates documentation from helm charts into markdown
files. The resulting files contain metadata about their respective chart
and a table with each of the chart's values, their defaults, and an
optional description parsed from comments.

PR: 297599
Approved by: arrowd (co-mentor)

(cherry picked from commit 691c574c56c433a75ef54e2e0b39aa72b61e732f)