Include CLI man pages on website

[tsandall]

Currently we do not have a comprehensive CLI reference on the website. This means that CLI users do not have an easy way to search for CLI options and examples when they want to do something new. Since we already generate man pages for the CLI, and the CLI descriptions contain examples and overviews of subcommands options, we could improve the situation (relatively easily) by generating HTML pages based on the CLI man pages. This was discussed in #3799. I am filing this issue to track the work as it's slightly more prescriptive about how to move forward.

CLI man pages were added by 4c81aa7. The tooling to generate the man pages have not changed since then. We should evaluate tools to generate HTML man pages and then integrate them into the docs/. To start, I'd like to see a single HTML page generated with subsections for each subcommand. The page can be called "CLI" and located under the "CORE DOCS" section of the website.